Squashed 'third_party/boostorg/optional/' content from commit 155ad59
Change-Id: I4ad7a1e7b295a6136c5a0d7b6c11700e76b939b5
git-subtree-dir: third_party/boostorg/optional
git-subtree-split: 155ad5911e5683cc87d34363f8304b60a30a8345
diff --git a/doc/html/boost_optional/reference/acknowledgements.html b/doc/html/boost_optional/reference/acknowledgements.html
new file mode 100644
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--- /dev/null
+++ b/doc/html/boost_optional/reference/acknowledgements.html
@@ -0,0 +1,131 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Acknowledgements</title>
+<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../index.html" title="Boost.Optional">
+<link rel="up" href="../../optional/reference.html" title="Reference">
+<link rel="prev" href="relnotes.html" title="Release Notes">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="relnotes.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h3 class="title">
+<a name="boost_optional.reference.acknowledgements"></a><a class="link" href="acknowledgements.html" title="Acknowledgements">Acknowledgements</a>
+</h3></div></div></div>
+<h5>
+<a name="boost_optional.reference.acknowledgements.h0"></a>
+ <span class="phrase"><a name="boost_optional.reference.acknowledgements.pre_formal_review"></a></span><a class="link" href="acknowledgements.html#boost_optional.reference.acknowledgements.pre_formal_review">Pre-formal
+ review</a>
+ </h5>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ Peter Dimov suggested the name 'optional', and was the first to point
+ out the need for aligned storage.
+ </li>
+<li class="listitem">
+ Douglas Gregor developed 'type_with_alignment', and later Eric Friedman
+ coded 'aligned_storage', which are the core of the optional class implementation.
+ </li>
+<li class="listitem">
+ Andrei Alexandrescu and Brian Parker also worked with aligned storage
+ techniques and their work influenced the current implementation.
+ </li>
+<li class="listitem">
+ Gennadiy Rozental made extensive and important comments which shaped
+ the design.
+ </li>
+<li class="listitem">
+ Vesa Karvonen and Douglas Gregor made quite useful comparisons between
+ optional, variant and any; and made other relevant comments.
+ </li>
+<li class="listitem">
+ Douglas Gregor and Peter Dimov commented on comparisons and evaluation
+ in boolean contexts.
+ </li>
+<li class="listitem">
+ Eric Friedman helped understand the issues involved with aligned storage,
+ move/copy operations and exception safety.
+ </li>
+<li class="listitem">
+ Many others have participated with useful comments: Aleksey Gurotov,
+ Kevlin Henney, David Abrahams, and others I can't recall.
+ </li>
+</ul></div>
+<h5>
+<a name="boost_optional.reference.acknowledgements.h1"></a>
+ <span class="phrase"><a name="boost_optional.reference.acknowledgements.post_formal_review"></a></span><a class="link" href="acknowledgements.html#boost_optional.reference.acknowledgements.post_formal_review">Post-formal
+ review</a>
+ </h5>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ William Kempf carefully considered the originally proposed interface
+ and suggested the new interface which is currently used. He also started
+ and fueled the discussion about the analogy optional<>/smart pointer
+ and about relational operators.
+ </li>
+<li class="listitem">
+ Peter Dimov, Joel de Guzman, David Abrahams, Tanton Gibbs and Ian Hanson
+ focused on the relational semantics of optional (originally undefined);
+ concluding with the fact that the pointer-like interface doesn't make
+ it a pointer so it shall have deep relational operators.
+ </li>
+<li class="listitem">
+ Augustus Saunders also explored the different relational semantics between
+ optional<> and a pointer and developed the OptionalPointee concept
+ as an aid against potential conflicts on generic code.
+ </li>
+<li class="listitem">
+ Joel de Guzman noticed that optional<> can be seen as an API on
+ top of variant<T,nil_t>.
+ </li>
+<li class="listitem">
+ Dave Gomboc explained the meaning and usage of the Haskell analog to
+ optional<>: the Maybe type constructor (analogy originally pointed
+ out by David Sankel).
+ </li>
+<li class="listitem">
+ Other comments were posted by Vincent Finn, Anthony Williams, Ed Brey,
+ Rob Stewart, and others.
+ </li>
+<li class="listitem">
+ Joel de Guzman made the case for the support of references and helped
+ with the proper semantics.
+ </li>
+<li class="listitem">
+ Mat Marcus shown the virtues of a value-oriented interface, influencing
+ the current design, and contributed the idea of "none".
+ </li>
+<li class="listitem">
+ Vladimir Batov's design of Boost.Convert library motivated the development
+ of value accessors for <code class="computeroutput"><span class="identifier">optional</span></code>:
+ functions <code class="computeroutput"><span class="identifier">value</span></code>, <code class="computeroutput"><span class="identifier">value_or</span></code>, <code class="computeroutput"><span class="identifier">value_or_eval</span></code>.
+ </li>
+</ul></div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2016 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="relnotes.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a>
+</div>
+</body>
+</html>
diff --git a/doc/html/boost_optional/reference/dependencies_and_portability.html b/doc/html/boost_optional/reference/dependencies_and_portability.html
new file mode 100644
index 0000000..5128861
--- /dev/null
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@@ -0,0 +1,84 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Dependencies and Portability</title>
+<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../index.html" title="Boost.Optional">
+<link rel="up" href="../../optional/reference.html" title="Reference">
+<link rel="prev" href="header__boost_optional_optional_hpp_/header__boost_optional_hpp_.html" title="Header <boost/optional.hpp>">
+<link rel="next" href="dependencies_and_portability/optional_reference_binding.html" title="Optional Reference Binding">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="header__boost_optional_optional_hpp_/header__boost_optional_hpp_.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="dependencies_and_portability/optional_reference_binding.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h3 class="title">
+<a name="boost_optional.reference.dependencies_and_portability"></a><a class="link" href="dependencies_and_portability.html" title="Dependencies and Portability">Dependencies
+ and Portability</a>
+</h3></div></div></div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.dependencies_and_portability.dependencies"></a><a class="link" href="dependencies_and_portability.html#boost_optional.reference.dependencies_and_portability.dependencies" title="Dependencies">Dependencies</a>
+</h4></div></div></div>
+<p>
+ The implementation uses the following other Boost modules:
+ </p>
+<div class="orderedlist"><ol class="orderedlist" type="1">
+<li class="listitem">
+ assert
+ </li>
+<li class="listitem">
+ config
+ </li>
+<li class="listitem">
+ core
+ </li>
+<li class="listitem">
+ detail
+ </li>
+<li class="listitem">
+ move
+ </li>
+<li class="listitem">
+ mpl
+ </li>
+<li class="listitem">
+ static_assert
+ </li>
+<li class="listitem">
+ throw_exception
+ </li>
+<li class="listitem">
+ type_traits
+ </li>
+<li class="listitem">
+ utility
+ </li>
+</ol></div>
+</div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2016 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="header__boost_optional_optional_hpp_/header__boost_optional_hpp_.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="dependencies_and_portability/optional_reference_binding.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>
diff --git a/doc/html/boost_optional/reference/dependencies_and_portability/optional_reference_binding.html b/doc/html/boost_optional/reference/dependencies_and_portability/optional_reference_binding.html
new file mode 100644
index 0000000..16c1637
--- /dev/null
+++ b/doc/html/boost_optional/reference/dependencies_and_portability/optional_reference_binding.html
@@ -0,0 +1,100 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Optional Reference Binding</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../dependencies_and_portability.html" title="Dependencies and Portability">
+<link rel="prev" href="../dependencies_and_portability.html" title="Dependencies and Portability">
+<link rel="next" href="../relnotes.html" title="Release Notes">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../dependencies_and_portability.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../dependencies_and_portability.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../relnotes.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.dependencies_and_portability.optional_reference_binding"></a><a class="link" href="optional_reference_binding.html" title="Optional Reference Binding">Optional
+ Reference Binding</a>
+</h4></div></div></div>
+<p>
+ On compilers that do not conform to Standard C++ rules of reference binding,
+ operations on optional references might give adverse results: rather than
+ binding a reference to a designated object they may create an unexpected
+ temporary and bind to it. Compilers known to have these deficiencies include
+ GCC versions 4.2, 4.3, 4.4, 4.5; QCC 4.4.2; MSVC versions 8.0, 9.0, 10.0,
+ 11.0, 12.0. On these compilers prefer using direct-initialization and copy
+ assignment of optional references to copy-initialization and assignment
+ from <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span></code>:
+ </p>
+<pre class="programlisting"><span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&></span> <span class="identifier">or1</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&></span> <span class="identifier">or2</span> <span class="special">=</span> <span class="identifier">i</span><span class="special">;</span> <span class="comment">// not portable</span>
+<span class="identifier">or1</span> <span class="special">=</span> <span class="identifier">i</span><span class="special">;</span> <span class="comment">// not portable</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&></span> <span class="identifier">or3</span><span class="special">(</span><span class="identifier">i</span><span class="special">);</span> <span class="comment">// portable</span>
+<span class="identifier">or1</span> <span class="special">=</span> <span class="identifier">optional</span><span class="special"><</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&>(</span><span class="identifier">i</span><span class="special">);</span> <span class="comment">// portable</span>
+</pre>
+<p>
+ In order to check if your compiler correctly implements reference binding
+ use this test program.
+ </p>
+<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">cassert</span><span class="special">></span>
+
+<span class="keyword">const</span> <span class="keyword">int</span> <span class="identifier">global_i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span>
+
+<span class="keyword">struct</span> <span class="identifier">TestingReferenceBinding</span>
+<span class="special">{</span>
+ <span class="identifier">TestingReferenceBinding</span><span class="special">(</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&</span> <span class="identifier">ii</span><span class="special">)</span>
+ <span class="special">{</span>
+ <span class="identifier">assert</span><span class="special">(&</span><span class="identifier">ii</span> <span class="special">==</span> <span class="special">&</span><span class="identifier">global_i</span><span class="special">);</span>
+ <span class="special">}</span>
+
+ <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">=(</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&</span> <span class="identifier">ii</span><span class="special">)</span>
+ <span class="special">{</span>
+ <span class="identifier">assert</span><span class="special">(&</span><span class="identifier">ii</span> <span class="special">==</span> <span class="special">&</span><span class="identifier">global_i</span><span class="special">);</span>
+ <span class="special">}</span>
+
+ <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">=(</span><span class="keyword">int</span><span class="special">&&)</span> <span class="comment">// remove this if your compiler doesn't have rvalue refs</span>
+ <span class="special">{</span>
+ <span class="identifier">assert</span><span class="special">(</span><span class="keyword">false</span><span class="special">);</span>
+ <span class="special">}</span>
+<span class="special">};</span>
+
+<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
+<span class="special">{</span>
+ <span class="keyword">const</span> <span class="keyword">int</span><span class="special">&</span> <span class="identifier">iref</span> <span class="special">=</span> <span class="identifier">global_i</span><span class="special">;</span>
+ <span class="identifier">assert</span><span class="special">(&</span><span class="identifier">iref</span> <span class="special">==</span> <span class="special">&</span><span class="identifier">global_i</span><span class="special">);</span>
+
+ <span class="identifier">TestingReferenceBinding</span> <span class="identifier">ttt</span> <span class="special">=</span> <span class="identifier">global_i</span><span class="special">;</span>
+ <span class="identifier">ttt</span> <span class="special">=</span> <span class="identifier">global_i</span><span class="special">;</span>
+
+ <span class="identifier">TestingReferenceBinding</span> <span class="identifier">ttt2</span> <span class="special">=</span> <span class="identifier">iref</span><span class="special">;</span>
+ <span class="identifier">ttt2</span> <span class="special">=</span> <span class="identifier">iref</span><span class="special">;</span>
+<span class="special">}</span>
+</pre>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2016 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../dependencies_and_portability.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../dependencies_and_portability.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../relnotes.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>
diff --git a/doc/html/boost_optional/reference/header__boost_optional_bad_optional_access_hpp_.html b/doc/html/boost_optional/reference/header__boost_optional_bad_optional_access_hpp_.html
new file mode 100644
index 0000000..363379c
--- /dev/null
+++ b/doc/html/boost_optional/reference/header__boost_optional_bad_optional_access_hpp_.html
@@ -0,0 +1,63 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Header <boost/optional/bad_optional_access.hpp></title>
+<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
+<link rel="home" href="../../index.html" title="Boost.Optional">
+<link rel="up" href="../../optional/reference.html" title="Reference">
+<link rel="prev" href="../../optional/reference.html" title="Reference">
+<link rel="next" href="header__boost_optional_bad_optional_access_hpp_/detailed_semantics.html" title="Detailed semantics">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td>
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+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header__boost_optional_bad_optional_access_hpp_/detailed_semantics.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h3 class="title">
+<a name="boost_optional.reference.header__boost_optional_bad_optional_access_hpp_"></a><a class="link" href="header__boost_optional_bad_optional_access_hpp_.html" title="Header <boost/optional/bad_optional_access.hpp>">Header
+ <boost/optional/bad_optional_access.hpp></a>
+</h3></div></div></div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_bad_optional_access_hpp_.synopsis"></a><a class="link" href="header__boost_optional_bad_optional_access_hpp_.html#boost_optional.reference.header__boost_optional_bad_optional_access_hpp_.synopsis" title="Synopsis">Synopsis</a>
+</h4></div></div></div>
+<p>
+</p>
+<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span>
+
+<span class="keyword">class</span> <span class="identifier">bad_optional_access</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">logic_error</span>
+<span class="special">{</span>
+<span class="keyword">public</span><span class="special">:</span>
+ <span class="identifier">bad_optional_access</span><span class="special">();</span> <a class="link" href="header__boost_optional_bad_optional_access_hpp_/detailed_semantics.html#reference_bad_optional_access_constructor"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+<span class="special">};</span>
+
+<span class="special">}</span> <span class="comment">// namespace boost</span>
+</pre>
+<p>
+ </p>
+</div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2018 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header__boost_optional_bad_optional_access_hpp_/detailed_semantics.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>
diff --git a/doc/html/boost_optional/reference/header__boost_optional_bad_optional_access_hpp_/detailed_semantics.html b/doc/html/boost_optional/reference/header__boost_optional_bad_optional_access_hpp_/detailed_semantics.html
new file mode 100644
index 0000000..b182324
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+++ b/doc/html/boost_optional/reference/header__boost_optional_bad_optional_access_hpp_/detailed_semantics.html
@@ -0,0 +1,60 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Detailed semantics</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
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+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_bad_optional_access_hpp_.detailed_semantics"></a><a class="link" href="detailed_semantics.html" title="Detailed semantics">Detailed
+ semantics</a>
+</h4></div></div></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<p>
+ <a name="reference_bad_optional_access_constructor"></a><code class="computeroutput"><span class="identifier">bad_optional_access</span><span class="special">();</span></code>
+ </p>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Constructs an object of class
+ <code class="computeroutput"><span class="identifier">bad_optional_access</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="identifier">what</span><span class="special">()</span></code> returns an implementation-defined
+ NTBS.
+ </li>
+</ul></div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2018 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../header__boost_optional_bad_optional_access_hpp_.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../header__boost_optional_bad_optional_access_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../io_header.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
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+</html>
diff --git a/doc/html/boost_optional/reference/header__boost_optional_hpp_.html b/doc/html/boost_optional/reference/header__boost_optional_hpp_.html
new file mode 100644
index 0000000..c8d6b9e
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+++ b/doc/html/boost_optional/reference/header__boost_optional_hpp_.html
@@ -0,0 +1,47 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Header <boost/optional.hpp></title>
+<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
+<link rel="home" href="../../index.html" title="Boost.Optional">
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+<link rel="next" href="../dependencies_and_portability.html" title="Dependencies and Portability">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
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+</div>
+<div class="section">
+<div class="titlepage"><div><div><h3 class="title">
+<a name="boost_optional.reference.header__boost_optional_hpp_"></a><a class="link" href="header__boost_optional_hpp_.html" title="Header <boost/optional.hpp>">Header
+ <boost/optional.hpp></a>
+</h3></div></div></div>
+<p>
+ This is an alias for header <a class="link" href="../../optional/reference/header__boost_optional_optional_hpp_.html#boost_optional.reference.header__boost_optional_optional_hpp_.header_optional_optional" title="Synopsis"><code class="computeroutput"><span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">optional</span><span class="special">/</span><span class="identifier">optional</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code></a>.
+ </p>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2018 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../dependencies_and_portability.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
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+</html>
diff --git a/doc/html/boost_optional/reference/header__boost_optional_optional_fwd_hpp_.html b/doc/html/boost_optional/reference/header__boost_optional_optional_fwd_hpp_.html
new file mode 100644
index 0000000..ee81dd9
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+++ b/doc/html/boost_optional/reference/header__boost_optional_optional_fwd_hpp_.html
@@ -0,0 +1,66 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Header <boost/optional/optional_fwd.hpp></title>
+<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
+<link rel="home" href="../../index.html" title="Boost.Optional">
+<link rel="up" href="../../optional/reference.html" title="Reference">
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+<link rel="next" href="../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header <boost/optional/optional.hpp>">
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+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="io_header/io_semantics.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h3 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_fwd_hpp_"></a><a class="link" href="header__boost_optional_optional_fwd_hpp_.html" title="Header <boost/optional/optional_fwd.hpp>">Header
+ <boost/optional/optional_fwd.hpp></a>
+</h3></div></div></div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_fwd_hpp_.synopsis"></a><a class="link" href="header__boost_optional_optional_fwd_hpp_.html#boost_optional.reference.header__boost_optional_optional_fwd_hpp_.synopsis" title="Synopsis">Synopsis</a>
+</h4></div></div></div>
+<p>
+</p>
+<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span>
+
+<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">class</span> <span class="identifier">optional</span> <span class="special">;</span>
+
+<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">void</span> <span class="identifier">swap</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="special">);</span>
+
+<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">struct</span> <span class="identifier">optional_swap_should_use_default_constructor</span> <span class="special">;</span>
+
+<span class="special">}</span> <span class="comment">// namespace boost</span>
+</pre>
+<p>
+ </p>
+<p>
+ This header only contains declarations.
+ </p>
+</div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2018 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="io_header/io_semantics.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>
diff --git a/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html
new file mode 100644
index 0000000..b7d25f5
--- /dev/null
+++ b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics.html
@@ -0,0 +1,2423 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Detailed Semantics</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header <boost/optional/optional.hpp>">
+<link rel="prev" href="header_optional_optional_refs.html" title="Optional References">
+<link rel="next" href="header__boost_optional_hpp_.html" title="Header <boost/optional.hpp>">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="header_optional_optional_refs.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header__boost_optional_hpp_.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics"></a><a class="link" href="detailed_semantics.html" title="Detailed Semantics">Detailed
+ Semantics</a>
+</h4></div></div></div>
+<p>
+ Because <code class="computeroutput"><span class="identifier">T</span></code> might be of reference
+ type, in the sequel, those entries whose semantic depends on <code class="computeroutput"><span class="identifier">T</span></code> being of reference type or not will
+ be distinguished using the following convention:
+ </p>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ If the entry reads: <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code><span class="emphasis"><em>(not
+ a ref)</em></span><code class="computeroutput"><span class="special">></span></code>,
+ the description corresponds only to the case where <code class="computeroutput"><span class="identifier">T</span></code>
+ is not of reference type.
+ </li>
+<li class="listitem">
+ If the entry reads: <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span></code>, the description corresponds
+ only to the case where <code class="computeroutput"><span class="identifier">T</span></code>
+ is of reference type.
+ </li>
+<li class="listitem">
+ If the entry reads: <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>, the description is the same for
+ both cases.
+ </li>
+</ul></div>
+<div class="note"><table border="0" summary="Note">
+<tr>
+<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../../doc/src/images/note.png"></td>
+<th align="left">Note</th>
+</tr>
+<tr><td align="left" valign="top"><p>
+ The following section contains various <code class="computeroutput"><span class="identifier">assert</span><span class="special">()</span></code> which are used only to show the postconditions
+ as sample code. It is not implied that the type <code class="computeroutput"><span class="identifier">T</span></code>
+ must support each particular expression but that if the expression is
+ supported, the implied condition holds.
+ </p></td></tr>
+</table></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<h6>
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics.h0"></a>
+ <span class="phrase"><a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics.optional_class_member_functions"></a></span><a class="link" href="detailed_semantics.html#boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics.optional_class_member_functions">optional
+ class member functions</a>
+ </h6>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">()</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Default-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">uninitialized</span>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> T's default constructor <span class="underline">is not</span> called.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_none_t"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">none_t</span> <span class="special">)</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Constructs an <code class="computeroutput"><span class="identifier">optional</span></code> uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">uninitialized</span>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>'s
+ default constructor <span class="underline">is not</span> called.
+ The expression <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none</span></code>
+ denotes an instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none_t</span></code>
+ that can be used as the parameter.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">none</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">n</span><span class="special">(</span><span class="identifier">none</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">n</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_copy_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
+ is <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Directly-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
+ and its value is a <span class="emphasis"><em>copy</em></span> of <code class="computeroutput"><span class="identifier">v</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span></code> throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span></code> is called.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">);</span></code> in that case, this constructor
+ has no effect.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">ref</span> <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Directly-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
+ and its value is an instance of an internal type wrapping the reference
+ <code class="computeroutput"><span class="identifier">ref</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">T</span><span class="special">&</span> <span class="identifier">vref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">vref</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="special">++</span> <span class="identifier">v</span> <span class="special">;</span> <span class="comment">// mutate referee</span>
+<span class="identifier">assert</span> <span class="special">(*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span><span class="special">);</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_move_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">v</span>
+ <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
+ is <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Directly-Move-Constructs an
+ <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
+ and its value is move-constructed from <code class="computeroutput"><span class="identifier">v</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code>
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code>
+ is called.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">);</span></code>
+ in that case, the state of <code class="computeroutput"><span class="identifier">v</span></code>
+ is determined by exception safety guarantees for <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span><span class="special">&&)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v1</span><span class="special">,</span> <span class="identifier">v2</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">v1</span><span class="special">));</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v2</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">T</span><span class="special">&&</span>
+ <span class="identifier">ref</span> <span class="special">)</span>
+ <span class="special">=</span> <span class="keyword">delete</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> This constructor is deleted
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_bool_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span>
+ <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span>
+ <span class="special">::</span><span class="identifier">optional</span><span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span>
+ <span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">v</span> <span class="special">)</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ If condition is true, same as:
+ </li></ul></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span>
+ <span class="special">::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ otherwise, same as:
+ </li></ul></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">()</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span>
+ <span class="special">::</span><span class="identifier">optional</span><span class="special">()</span></code>
+ </p></blockquote></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">rhs</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_copy_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
+ is <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Copy-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> If rhs is initialized,
+ <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initialized and its value is a <span class="emphasis"><em>copy</em></span> of the
+ value of <code class="computeroutput"><span class="identifier">rhs</span></code>; else
+ <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span></code> throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If rhs is initialized, <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code>
+ is called.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">);</span></code> in that case, this constructor
+ has no effect.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">uninit</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">uninit</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init</span><span class="special">(</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span>
+ <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Copy-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initialized and its value is another reference to the same object
+ referenced by <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>;
+ else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> will refer to the same object
+ (they alias).
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">uninit</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">uninit</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span>
+
+<span class="identifier">T</span> <span class="identifier">v</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">ref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init</span><span class="special">(</span><span class="identifier">ref</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">v</span> <span class="special">=</span> <span class="number">3</span> <span class="special">;</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_move_constructor_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span><span class="special">&&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span></code><span class="emphasis"><em>see below</em></span><code class="computeroutput"><span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
+ is <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Move-constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initialized and its value is move constructed from <code class="computeroutput"><span class="identifier">rhs</span></code>; else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code>
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> The expression inside <code class="computeroutput"><span class="keyword">noexcept</span></code> is equivalent to <code class="computeroutput"><span class="identifier">is_nothrow_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="special">&&</span>
+ <span class="special">)</span></code> is called.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">);</span></code>
+ in that case, <code class="computeroutput"><span class="identifier">rhs</span></code> remains
+ initialized and the value of <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by exception safety
+ of <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span><span class="special">&&)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">uninit</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">uninit</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">init</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">uniqye_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="keyword">new</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">init</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="keyword">nullptr</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init2</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">optional</span> <span class="special">&&</span>
+ <span class="identifier">rhs</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Move-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initialized and its value is another reference to the same object
+ referenced by <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>;
+ else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> will refer to the same object
+ (they alias).
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">uninit</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">uninit</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span>
+
+<span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">v</span><span class="special">(</span><span class="keyword">new</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">init</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">init</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="special">*</span><span class="identifier">v</span> <span class="special">=</span> <span class="number">3</span> <span class="special">;</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init2</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Copy-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initialized and its value is a <span class="emphasis"><em>copy</em></span> of the
+ value of rhs converted to type <code class="computeroutput"><span class="identifier">T</span></code>;
+ else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span></code> throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span></code> is called if <code class="computeroutput"><span class="identifier">rhs</span></code> is initialized, which requires
+ a valid conversion from <code class="computeroutput"><span class="identifier">U</span></code>
+ to <code class="computeroutput"><span class="identifier">T</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">);</span></code> in that case, this constructor
+ has no effect.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span><span class="number">123.4</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="number">123.4</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span><span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="number">123</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_move_constructor_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">>&&</span>
+ <span class="identifier">rhs</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Move-constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initialized and its value is move-constructed from <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>;
+ else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">)</span></code>
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">)</span></code>
+ is called if <code class="computeroutput"><span class="identifier">rhs</span></code> is
+ initialized, which requires a valid conversion from <code class="computeroutput"><span class="identifier">U</span></code>
+ to <code class="computeroutput"><span class="identifier">T</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">);</span></code>
+ in that case, <code class="computeroutput"><span class="identifier">rhs</span></code> remains
+ initialized and the value of <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by exception safety
+ guarantee of <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span>
+ <span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span><span class="number">123.4</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="number">123.4</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">x</span><span class="special">))</span> <span class="special">;</span>
+<span class="identifier">assert</span><span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="number">123</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_factory"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">InPlaceFactory</span><span class="special">></span>
+ <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">InPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">TypedInPlaceFactory</span><span class="special">></span>
+ <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">TypedInPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Constructs an <code class="computeroutput"><span class="identifier">optional</span></code> with a value of <code class="computeroutput"><span class="identifier">T</span></code> obtained from the factory.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
+ and its value is <span class="emphasis"><em>directly given</em></span> from the factory
+ <code class="computeroutput"><span class="identifier">f</span></code> (i.e., the value
+ <span class="underline">is not copied</span>).
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever the <code class="computeroutput"><span class="identifier">T</span></code> constructor called by the factory
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> See <a class="link" href="../../tutorial/in_place_factories.html" title="In-Place Factories">In-Place
+ Factories</a>
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during the call to the <code class="computeroutput"><span class="identifier">T</span></code>
+ constructor used by the factory; in that case, this constructor has
+ no effect.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">C</span> <span class="special">{</span> <span class="identifier">C</span> <span class="special">(</span> <span class="keyword">char</span><span class="special">,</span> <span class="keyword">double</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">)</span> <span class="special">;</span> <span class="special">}</span> <span class="special">;</span>
+
+<span class="identifier">C</span> <span class="identifier">v</span><span class="special">(</span><span class="char">'A'</span><span class="special">,</span><span class="number">123.4</span><span class="special">,</span><span class="string">"hello"</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">C</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span> <span class="identifier">in_place</span> <span class="special">(</span><span class="char">'A'</span><span class="special">,</span> <span class="number">123.4</span><span class="special">,</span> <span class="string">"hello"</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// InPlaceFactory used</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">C</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span> <span class="identifier">in_place</span><span class="special"><</span><span class="identifier">C</span><span class="special">>(</span><span class="char">'A'</span><span class="special">,</span> <span class="number">123.4</span><span class="special">,</span> <span class="string">"hello"</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// TypedInPlaceFactory used</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_equal_none_t"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">none_t</span>
+ <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized destroys its contained
+ value.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_equal_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">rhs</span> <span class="special">)</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Assigns the value <code class="computeroutput"><span class="identifier">rhs</span></code> to an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and its value is
+ a <span class="emphasis"><em>copy</em></span> of <code class="computeroutput"><span class="identifier">rhs</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span></code> or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&)</span></code>
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s assignment operator is used,
+ otherwise, its copy-constructor is used.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> In the event of
+ an exception, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified
+ as far as <code class="computeroutput"><span class="identifier">optional</span></code>
+ is concerned (it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s
+ <code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>).
+ If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s
+ <span class="emphasis"><em>copy constructor</em></span> fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">T</span> <span class="identifier">y</span><span class="special">;</span>
+<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">y</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">y</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> (Re)binds the wrapped reference.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and it references
+ the same object referenced by <code class="computeroutput"><span class="identifier">rhs</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, it is <span class="emphasis"><em>rebound</em></span>
+ to the new object. See <a class="link" href="../../tutorial/rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">here</a>
+ for details on this behavior.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
+<span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">ra</span><span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">rb</span> <span class="special">;</span> <span class="comment">// binds 'def' to 'b' through 'rb'</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">b</span> <span class="special">)</span> <span class="special">;</span>
+<span class="special">*</span><span class="identifier">def</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span> <span class="comment">// changes the value of 'b' to a copy of the value of 'a'</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">b</span> <span class="special">==</span> <span class="identifier">a</span> <span class="special">)</span> <span class="special">;</span>
+<span class="keyword">int</span> <span class="identifier">c</span> <span class="special">=</span> <span class="number">3</span><span class="special">;</span>
+<span class="keyword">int</span><span class="special">&</span> <span class="identifier">rc</span> <span class="special">=</span> <span class="identifier">c</span> <span class="special">;</span>
+<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">rc</span> <span class="special">;</span> <span class="comment">// REBINDS to 'c' through 'rc'</span>
+<span class="identifier">c</span> <span class="special">=</span> <span class="number">4</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="number">4</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_move_equal_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Moves the value <code class="computeroutput"><span class="identifier">rhs</span></code> to an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and its value is
+ moved from <code class="computeroutput"><span class="identifier">rhs</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code>
+ or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span> <span class="special">&&)</span></code>
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s move-assignment operator is used,
+ otherwise, its move-constructor is used.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> In the event of
+ an exception, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified
+ as far as <code class="computeroutput"><span class="identifier">optional</span></code>
+ is concerned (it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s
+ <code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>).
+ If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s
+ <span class="emphasis"><em>move constructor</em></span> fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">T</span> <span class="identifier">y1</span><span class="special">,</span> <span class="identifier">y2</span><span class="special">,</span> <span class="identifier">yR</span><span class="special">;</span>
+<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">y1</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">yR</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">y2</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">yR</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="special">=</span>
+ <span class="keyword">delete</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> This assignment operator is
+ deleted.
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_equal_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">rhs</span> <span class="special">)</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ is <a href="../../../../../../utility/CopyConstructible.html" target="_top"><code class="computeroutput"><span class="identifier">CopyConstructible</span></code></a> and <code class="computeroutput"><span class="identifier">CopyAssignable</span></code>.
+ </li>
+<li class="listitem">
+<p class="simpara">
+ <span class="bold"><strong>Effects:</strong></span>
+ </p>
+<div class="informaltable"><table class="table">
+<colgroup>
+<col>
+<col>
+<col>
+</colgroup>
+<thead><tr></tr></thead>
+<tbody>
+<tr>
+<td>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ assigns <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
+ to the contained value
+ </p>
+ </td>
+<td>
+ <p>
+ initializes the contained value as if direct-initializing
+ an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+ with <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ does not contain a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>
+ </p>
+ </td>
+<td>
+ <p>
+ no effect
+ </p>
+ </td>
+</tr>
+</tbody>
+</table></div>
+</li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>;
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> If any exception
+ is thrown, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">rhs</span></code>
+ remains unchanged. If an exception is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s copy constructor, no effect.
+ If an exception is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s
+ copy assignment, the state of its contained value is as defined by
+ the exception safety guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s
+ copy assignment.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
+
+<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span>
+<span class="comment">// previous value (copy of 'v') destroyed from within 'opt'.</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span>
+ <span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> (Re)binds thee wrapped reference.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initialized and it references the same object referenced by <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>;
+ otherwise, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is uninitialized (and references no object).
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized and so is <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>,
+ <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is <span class="emphasis"><em>rebound</em></span> to the new object. See <a class="link" href="../../tutorial/rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">here</a>
+ for details on this behavior.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
+<span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">ora</span><span class="special">(</span><span class="identifier">ra</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">orb</span><span class="special">(</span><span class="identifier">rb</span><span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">orb</span> <span class="special">;</span> <span class="comment">// binds 'def' to 'b' through 'rb' wrapped within 'orb'</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">b</span> <span class="special">)</span> <span class="special">;</span>
+<span class="special">*</span><span class="identifier">def</span> <span class="special">=</span> <span class="identifier">ora</span> <span class="special">;</span> <span class="comment">// changes the value of 'b' to a copy of the value of 'a'</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">b</span> <span class="special">==</span> <span class="identifier">a</span> <span class="special">)</span> <span class="special">;</span>
+<span class="keyword">int</span> <span class="identifier">c</span> <span class="special">=</span> <span class="number">3</span><span class="special">;</span>
+<span class="keyword">int</span><span class="special">&</span> <span class="identifier">rc</span> <span class="special">=</span> <span class="identifier">c</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">orc</span><span class="special">(</span><span class="identifier">rc</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">ora</span> <span class="special">=</span> <span class="identifier">orc</span> <span class="special">;</span> <span class="comment">// REBINDS ora to 'c' through 'rc'</span>
+<span class="identifier">c</span> <span class="special">=</span> <span class="number">4</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">ora</span> <span class="special">==</span> <span class="number">4</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_move_equal_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span></code><span class="emphasis"><em>see below</em></span><code class="computeroutput"><span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ is <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>
+ and <code class="computeroutput"><span class="identifier">MoveAssignable</span></code>.
+ </li>
+<li class="listitem">
+<p class="simpara">
+ <span class="bold"><strong>Effects:</strong></span>
+ </p>
+<div class="informaltable"><table class="table">
+<colgroup>
+<col>
+<col>
+<col>
+</colgroup>
+<thead><tr></tr></thead>
+<tbody>
+<tr>
+<td>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ assigns <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code> to the contained value
+ </p>
+ </td>
+<td>
+ <p>
+ initializes the contained value as if direct-initializing
+ an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+ with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ does not contain a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>
+ </p>
+ </td>
+<td>
+ <p>
+ no effect
+ </p>
+ </td>
+</tr>
+</tbody>
+</table></div>
+</li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>;
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> The expression inside <code class="computeroutput"><span class="keyword">noexcept</span></code> is equivalent to <code class="computeroutput"><span class="identifier">is_nothrow_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span> <span class="special">&&</span>
+ <span class="identifier">is_nothrow_move_assignable</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> If any exception
+ is thrown, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">rhs</span></code>
+ remains unchanged. If an exception is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s move constructor, the state of
+ <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
+ is determined by the exception safety guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s
+ move constructor. If an exception is thrown during the call to T's
+ move-assignment, the state of <code class="computeroutput"><span class="special">**</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by the exception
+ safety guarantee of T's move assignment.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
+
+<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span>
+ <span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Same as <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">rhs</span> <span class="special">)</span></code>.
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_equal_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+<p class="simpara">
+ <span class="bold"><strong>Effect:</strong></span>
+ </p>
+<div class="informaltable"><table class="table">
+<colgroup>
+<col>
+<col>
+<col>
+</colgroup>
+<thead><tr></tr></thead>
+<tbody>
+<tr>
+<td>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ assigns <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
+ to the contained value
+ </p>
+ </td>
+<td>
+ <p>
+ initializes the contained value as if direct-initializing
+ an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+ with <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ does not contain a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>
+ </p>
+ </td>
+<td>
+ <p>
+ no effect
+ </p>
+ </td>
+</tr>
+</tbody>
+</table></div>
+</li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> If any exception
+ is thrown, the result of the expression <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code> remains unchanged. If an exception
+ is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s
+ constructor, no effect. If an exception is thrown during the call to
+ <code class="computeroutput"><span class="identifier">T</span></code>'s assignment, the
+ state of its contained value is as defined by the exception safety
+ guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s copy
+ assignment.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt0</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">opt1</span><span class="special">;</span>
+
+<span class="identifier">opt1</span> <span class="special">=</span> <span class="identifier">opt0</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt1</span> <span class="special">==</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_move_equal_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">>&&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+<p class="simpara">
+ <span class="bold"><strong>Effect:</strong></span>
+ </p>
+<div class="informaltable"><table class="table">
+<colgroup>
+<col>
+<col>
+<col>
+</colgroup>
+<thead><tr></tr></thead>
+<tbody>
+<tr>
+<td>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ assigns <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code> to the contained value
+ </p>
+ </td>
+<td>
+ <p>
+ initializes the contained value as if direct-initializing
+ an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+ with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ does not contain a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>
+ </p>
+ </td>
+<td>
+ <p>
+ no effect
+ </p>
+ </td>
+</tr>
+</tbody>
+</table></div>
+</li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> If any exception
+ is thrown, the result of the expression <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code> remains unchanged. If an exception
+ is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s
+ constructor, no effect. If an exception is thrown during the call to
+ <code class="computeroutput"><span class="identifier">T</span></code>'s assignment, the
+ state of its contained value is as defined by the exception safety
+ guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s copy
+ assignment.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt0</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">opt1</span><span class="special">;</span>
+
+<span class="identifier">opt1</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">opt0</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt0</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt1</span> <span class="special">)</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt1</span> <span class="special">==</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_emplace"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">></span>
+ <span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">emplace</span><span class="special">(</span>
+ <span class="identifier">Args</span><span class="special">...&&</span>
+ <span class="identifier">args</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> The compiler supports rvalue
+ references and variadic templates.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized calls <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span> <span class="special">=</span> <span class="identifier">none</span></code>.
+ Then initializes in-place the contained value as if direct-initializing
+ an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+ with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">Args</span><span class="special">>(</span><span class="identifier">args</span><span class="special">)...</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever the selected <code class="computeroutput"><span class="identifier">T</span></code>'s constructor throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> If an exception
+ is thrown during the initialization of <code class="computeroutput"><span class="identifier">T</span></code>,
+ <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is <span class="emphasis"><em>uninitialized</em></span>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ need not be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>
+ or <code class="computeroutput"><span class="identifier">MoveAssignable</span></code>.
+ On compilers that do not support variadic templates, the signature
+ falls back to two overloads:<code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span>
+ <span class="identifier">Arg</span><span class="special">></span>
+ <span class="keyword">void</span> <span class="identifier">emplace</span><span class="special">(</span><span class="identifier">Arg</span><span class="special">&&</span> <span class="identifier">arg</span><span class="special">)</span></code> and <code class="computeroutput"><span class="keyword">void</span>
+ <span class="identifier">emplace</span><span class="special">()</span></code>.
+ On compilers that do not support rvalue references, the signature falls
+ back to three overloads: taking <code class="computeroutput"><span class="keyword">const</span></code>
+ and non-<code class="computeroutput"><span class="keyword">const</span></code> lvalue reference,
+ and third with empty function argument list.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">const</span> <span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">;</span>
+<span class="identifier">opt</span><span class="special">.</span><span class="identifier">emplace</span><span class="special">(</span><span class="number">0</span><span class="special">);</span> <span class="comment">// create in-place using ctor T(int)</span>
+<span class="identifier">opt</span><span class="special">.</span><span class="identifier">emplace</span><span class="special">();</span> <span class="comment">// destroy previous and default-construct another T</span>
+<span class="identifier">opt</span><span class="special">.</span><span class="identifier">emplace</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> <span class="comment">// destroy and copy-construct in-place (no assignment called)</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_equal_factory"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">InPlaceFactory</span><span class="special">></span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">InPlaceFactory</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">f</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">TypedInPlaceFactory</span><span class="special">></span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">TypedInPlaceFactory</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">f</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Assigns an <code class="computeroutput"><span class="identifier">optional</span></code>
+ with a value of <code class="computeroutput"><span class="identifier">T</span></code> obtained
+ from the factory.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
+ and its value is <span class="emphasis"><em>directly given</em></span> from the factory
+ <code class="computeroutput"><span class="identifier">f</span></code> (i.e., the value
+ <span class="underline">is not copied</span>).
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever the <code class="computeroutput"><span class="identifier">T</span></code> constructor called by the factory
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> See <a class="link" href="../../tutorial/in_place_factories.html" title="In-Place Factories">In-Place
+ Factories</a>
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during the call to the <code class="computeroutput"><span class="identifier">T</span></code>
+ constructor used by the factory; in that case, the <code class="computeroutput"><span class="identifier">optional</span></code>
+ object will be reset to be <span class="emphasis"><em>uninitialized</em></span>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_reset_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">reset</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Deprecated:</strong></span> same as <code class="computeroutput"><span class="keyword">operator</span><span class="special">=</span>
+ <span class="special">(</span> <span class="identifier">T</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">v</span><span class="special">)</span>
+ <span class="special">;</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_reset"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reset</span><span class="special">()</span> <span class="keyword">noexcept</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Deprecated:</strong></span> Same as <code class="computeroutput"><span class="keyword">operator</span><span class="special">=(</span>
+ <span class="identifier">none_t</span> <span class="special">);</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_get"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get</span><span class="special">()</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">get</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span>
+ <span class="special">&)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> A reference to the contained
+ value
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The requirement is asserted
+ via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">get</span><span class="special">()</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">get</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="special">&)</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <span class="underline">The</span>
+ reference contained.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The requirement is asserted
+ via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_asterisk"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">*()</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">*()</span> <span class="special">&;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> A reference to the contained
+ value
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The requirement is asserted
+ via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
+ On compilers that do not support ref-qualifiers on member functions
+ these two overloads are replaced with the classical two: a <code class="computeroutput"><span class="keyword">const</span></code> and non-<code class="computeroutput"><span class="keyword">const</span></code>
+ member functions.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span>
+<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">u</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">opt</span><span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">u</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">T</span> <span class="identifier">w</span> <span class="special">;</span>
+<span class="special">*</span><span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">w</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">w</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_asterisk_move"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">*()</span> <span class="special">&&;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">val</span><span class="special">);</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The requirement is asserted
+ via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
+ On compilers that do not support ref-qualifiers on member functions
+ this overload is not present.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">*()</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">*()</span>
+ <span class="special">&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">*()</span>
+ <span class="special">&&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <span class="underline">The</span>
+ reference contained.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The requirement is asserted
+ via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
+ On compilers that do not support ref-qualifiers on member functions
+ these three overloads are replaced with the classical two: a <code class="computeroutput"><span class="keyword">const</span></code> and non-<code class="computeroutput"><span class="keyword">const</span></code>
+ member functions.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&</span> <span class="identifier">vref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">vref</span> <span class="special">);</span>
+<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">vref2</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">opt</span><span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">vref2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="special">++</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span><span class="special">()</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span><span class="special">()</span> <span class="special">&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">?</span> <span class="special">*</span><span class="identifier">val</span> <span class="special">:</span> <span class="keyword">throw</span> <span class="identifier">bad_optional_access</span><span class="special">();</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ ref-qualifiers on member functions these two overloads are replaced
+ with the classical two: a <code class="computeroutput"><span class="keyword">const</span></code>
+ and non-<code class="computeroutput"><span class="keyword">const</span></code> member functions.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o0</span><span class="special">,</span> <span class="identifier">o1</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span><span class="special">.</span><span class="identifier">value</span><span class="special">()</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">);</span>
+
+<span class="keyword">try</span> <span class="special">{</span>
+ <span class="identifier">o0</span><span class="special">.</span><span class="identifier">value</span><span class="special">();</span> <span class="comment">// throws</span>
+ <span class="identifier">assert</span> <span class="special">(</span> <span class="keyword">false</span> <span class="special">);</span>
+<span class="special">}</span>
+<span class="keyword">catch</span><span class="special">(</span><span class="identifier">bad_optional_access</span><span class="special">&)</span> <span class="special">{</span>
+ <span class="identifier">assert</span> <span class="special">(</span> <span class="keyword">true</span> <span class="special">);</span>
+<span class="special">}</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_value_move"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span><span class="special">()</span> <span class="special">&&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">?</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">val</span><span class="special">)</span> <span class="special">:</span> <span class="keyword">throw</span> <span class="identifier">bad_optional_access</span><span class="special">();</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ ref-qualifiers on member functions this overload is not present.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_value_or"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or</span><span class="special">(</span><span class="identifier">U</span> <span class="special">&&</span>
+ <span class="identifier">v</span><span class="special">)</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">if</span> <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="special">**</span><span class="keyword">this</span><span class="special">;</span> <span class="keyword">else</span> <span class="keyword">return</span>
+ <span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">);</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> If <code class="computeroutput"><span class="identifier">T</span></code>
+ is not <a href="../../../../../../utility/CopyConstructible.html" target="_top"><code class="computeroutput"><span class="identifier">CopyConstructible</span></code></a> or <code class="computeroutput"><span class="identifier">U</span> <span class="special">&&</span></code>
+ is not convertible to <code class="computeroutput"><span class="identifier">T</span></code>,
+ the program is ill-formed.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ ref-qualifiers on member functions this overload is replaced with the
+ <code class="computeroutput"><span class="keyword">const</span></code>-qualified member
+ function. On compilers without rvalue reference support the type of
+ <code class="computeroutput"><span class="identifier">v</span></code> becomes <code class="computeroutput"><span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span></code>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_value_or_move"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or</span><span class="special">(</span><span class="identifier">U</span> <span class="special">&&</span>
+ <span class="identifier">v</span><span class="special">)</span>
+ <span class="special">&&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">if</span> <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(**</span><span class="keyword">this</span><span class="special">);</span> <span class="keyword">else</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">);</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> If <code class="computeroutput"><span class="identifier">T</span></code>
+ is not <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>
+ or <code class="computeroutput"><span class="identifier">U</span> <span class="special">&&</span></code>
+ is not convertible to <code class="computeroutput"><span class="identifier">T</span></code>,
+ the program is ill-formed.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ ref-qualifiers on member functions this overload is not present.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_value_or_call"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">F</span> <span class="identifier">f</span><span class="special">)</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ is <a href="../../../../../../utility/CopyConstructible.html" target="_top"><code class="computeroutput"><span class="identifier">CopyConstructible</span></code></a> and <code class="computeroutput"><span class="identifier">F</span></code> models a <a href="http://www.sgi.com/tech/stl/Generator.html" target="_top"><code class="computeroutput"><span class="identifier">Generator</span></code></a> whose result type
+ is convertible to <code class="computeroutput"><span class="identifier">T</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> <code class="computeroutput"><span class="keyword">if</span>
+ <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="special">**</span><span class="keyword">this</span><span class="special">;</span> <span class="keyword">else</span> <span class="keyword">return</span> <span class="identifier">f</span><span class="special">();</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ ref-qualifiers on member functions this overload is replaced with the
+ <code class="computeroutput"><span class="keyword">const</span></code>-qualified member
+ function.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">complain_and_0</span><span class="special">()</span>
+<span class="special">{</span>
+ <span class="identifier">clog</span> <span class="special"><<</span> <span class="string">"no value returned, using default"</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span>
+ <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
+<span class="special">}</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">o1</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">oN</span> <span class="special">=</span> <span class="identifier">none</span><span class="special">;</span>
+
+<span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="identifier">o1</span><span class="special">.</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">complain_and_0</span><span class="special">);</span> <span class="comment">// fun not called</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">i</span> <span class="special">==</span> <span class="number">1</span><span class="special">);</span>
+
+<span class="keyword">int</span> <span class="identifier">j</span> <span class="special">=</span> <span class="identifier">oN</span><span class="special">.</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">complain_and_0</span><span class="special">);</span> <span class="comment">// fun called</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">i</span> <span class="special">==</span> <span class="number">0</span><span class="special">);</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_value_or_call_move"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">F</span> <span class="identifier">f</span><span class="special">)</span> <span class="special">&&</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ is <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>
+ and <code class="computeroutput"><span class="identifier">F</span></code> models a <a href="http://www.sgi.com/tech/stl/Generator.html" target="_top"><code class="computeroutput"><span class="identifier">Generator</span></code></a>
+ whose result type is convertible to <code class="computeroutput"><span class="identifier">T</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> <code class="computeroutput"><span class="keyword">if</span>
+ <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(**</span><span class="keyword">this</span><span class="special">);</span> <span class="keyword">else</span> <span class="keyword">return</span>
+ <span class="identifier">f</span><span class="special">();</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ ref-qualifiers on member functions this overload is not present.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_get_value_or_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_value_or</span><span class="special">(</span>
+ <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="keyword">default</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_value_or</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&</span> <span class="keyword">default</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">get_optional_value_or</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">o</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="keyword">default</span> <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get_optional_value_or</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>&</span>
+ <span class="identifier">o</span><span class="special">,</span>
+ <span class="identifier">T</span><span class="special">&</span>
+ <span class="keyword">default</span> <span class="special">)</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Deprecated:</strong></span> Use <code class="computeroutput"><span class="identifier">value_or</span><span class="special">()</span></code> instead.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> A reference to the contained
+ value, if any, or <code class="computeroutput"><span class="keyword">default</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">,</span> <span class="identifier">z</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span><span class="special">;</span>
+<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">=</span> <span class="identifier">def</span><span class="special">.</span><span class="identifier">get_value_or</span><span class="special">(</span><span class="identifier">z</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">y</span> <span class="special">==</span> <span class="identifier">z</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span>
+<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">u</span> <span class="special">=</span> <span class="identifier">get_optional_value_or</span><span class="special">(</span><span class="identifier">opt</span><span class="special">,</span><span class="identifier">z</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">u</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">u</span> <span class="special">!=</span> <span class="identifier">z</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_get_ptr"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_ptr</span><span class="special">()</span>
+ <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">*</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span>
+ <span class="keyword">const</span><span class="special">*</span>
+ <span class="identifier">get_pointer</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">get_pointer</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span>
+ <span class="special">&)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized, a pointer to the
+ contained value; else <code class="computeroutput"><span class="number">0</span></code>
+ (<span class="emphasis"><em>null</em></span>).
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The contained value is permanently
+ stored within <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>,
+ so you should not hold nor delete this pointer
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span> <span class="identifier">copt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">T</span><span class="special">*</span> <span class="identifier">p</span> <span class="special">=</span> <span class="identifier">opt</span><span class="special">.</span><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">;</span>
+<span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">cp</span> <span class="special">=</span> <span class="identifier">copt</span><span class="special">.</span><span class="identifier">get_ptr</span><span class="special">();</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">p</span> <span class="special">==</span> <span class="identifier">get_pointer</span><span class="special">(</span><span class="identifier">opt</span><span class="special">)</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">cp</span> <span class="special">==</span> <span class="identifier">get_pointer</span><span class="special">(</span><span class="identifier">copt</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_arrow"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span> <span class="special">->()</span>
+ <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">*</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span>
+ <span class="special">->()</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> A pointer to the contained
+ value.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The requirement is asserted
+ via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">X</span> <span class="special">{</span> <span class="keyword">int</span> <span class="identifier">mdata</span> <span class="special">;</span> <span class="special">}</span> <span class="special">;</span>
+<span class="identifier">X</span> <span class="identifier">x</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">X</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
+<span class="identifier">opt</span><span class="special">-></span><span class="identifier">mdata</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_bool"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span>
+ <span class="keyword">bool</span><span class="special">()</span>
+ <span class="keyword">const</span> <span class="keyword">noexcept</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">!=</span> <span class="number">0</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ explicit conversion operators this falls back to safe-bool idiom.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def</span> <span class="special">==</span> <span class="number">0</span> <span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">!=</span> <span class="number">0</span> <span class="special">);</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_not"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">noexcept</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized, <code class="computeroutput"><span class="keyword">true</span></code>; else <code class="computeroutput"><span class="keyword">false</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> This operator is provided for
+ those compilers which can't use the <span class="emphasis"><em>unspecified-bool-type
+ operator</em></span> in certain boolean contexts.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">opt</span> <span class="special">);</span>
+<span class="special">*</span><span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">some_T</span> <span class="special">;</span>
+
+<span class="comment">// Notice the "double-bang" idiom here.</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!!</span><span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_is_initialized"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_initialized</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Deprecated:</strong></span> Same as <code class="computeroutput"><span class="keyword">explicit</span> <span class="keyword">operator</span>
+ <span class="keyword">bool</span> <span class="special">()</span>
+ <span class="special">;</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<h6>
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics.h1"></a>
+ <span class="phrase"><a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics.free_functions"></a></span><a class="link" href="detailed_semantics.html#boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics.free_functions">Free
+ functions</a>
+ </h6>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_make_optional_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="identifier">make_optional</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span></code> for the <span class="emphasis"><em>deduced</em></span>
+ type <code class="computeroutput"><span class="identifier">T</span></code> of <code class="computeroutput"><span class="identifier">v</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">void</span> <span class="identifier">foo</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">foo</span> <span class="special">(</span> <span class="identifier">make_optional</span><span class="special">(</span><span class="number">1</span><span class="special">+</span><span class="number">1</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> <span class="comment">// Creates an optional<int></span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_make_optional_bool_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="identifier">make_optional</span><span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span>
+ <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">condition</span><span class="special">,</span><span class="identifier">v</span><span class="special">)</span></code> for the <span class="emphasis"><em>deduced</em></span>
+ type <code class="computeroutput"><span class="identifier">T</span></code> of <code class="computeroutput"><span class="identifier">v</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">calculate_foo</span><span class="special">()</span>
+<span class="special">{</span>
+ <span class="keyword">double</span> <span class="identifier">val</span> <span class="special">=</span> <span class="identifier">compute_foo</span><span class="special">();</span>
+ <span class="keyword">return</span> <span class="identifier">make_optional</span><span class="special">(</span><span class="identifier">is_not_nan_and_finite</span><span class="special">(</span><span class="identifier">val</span><span class="special">),</span><span class="identifier">val</span><span class="special">);</span>
+<span class="special">}</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">v</span> <span class="special">=</span> <span class="identifier">calculate_foo</span><span class="special">();</span>
+<span class="keyword">if</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">v</span> <span class="special">)</span>
+ <span class="identifier">error</span><span class="special">(</span><span class="string">"foo wasn't computed"</span><span class="special">);</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">==</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ shall meet requirements of <a href="http://www.sgi.com/tech/stl/EqualityComparable.html" target="_top"><code class="computeroutput"><span class="identifier">EqualityComparable</span></code></a>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> If both <code class="computeroutput"><span class="identifier">x</span></code>
+ and <code class="computeroutput"><span class="identifier">y</span></code> are initialized,
+ <code class="computeroutput"><span class="special">(*</span><span class="identifier">x</span>
+ <span class="special">==</span> <span class="special">*</span><span class="identifier">y</span><span class="special">)</span></code>.
+ If only <code class="computeroutput"><span class="identifier">x</span></code> or <code class="computeroutput"><span class="identifier">y</span></code> is initialized, <code class="computeroutput"><span class="keyword">false</span></code>.
+ If both are uninitialized, <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> This definition guarantees
+ that <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>
+ not containing a value is compared unequal to any <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> containing any value, and equal
+ to any other <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> not containing a value. Pointers
+ have shallow relational operators while <code class="computeroutput"><span class="identifier">optional</span></code>
+ has deep relational operators. Do not use <code class="computeroutput"><span class="keyword">operator</span><span class="special">==</span></code> directly in generic code which expect
+ to be given either an <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> or a pointer; use <a href="../../../../../../utility/OptionalPointee.html#equal" target="_top"><code class="computeroutput"><span class="identifier">equal_pointees</span><span class="special">()</span></code></a>
+ instead
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">oN</span><span class="special">,</span> <span class="identifier">oN_</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o1</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">)),</span> <span class="identifier">o1_</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">));</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o2</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">));</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">==</span> <span class="identifier">oN</span> <span class="special">);</span> <span class="comment">// Identity implies equality</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">==</span> <span class="identifier">o1</span> <span class="special">);</span> <span class="comment">//</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">==</span> <span class="identifier">oN_</span> <span class="special">);</span> <span class="comment">// Both uninitialized compare equal</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">!=</span> <span class="identifier">o1</span> <span class="special">);</span> <span class="comment">// Initialized unequal to initialized.</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">==</span> <span class="identifier">o1_</span> <span class="special">);</span> <span class="comment">// Both initialized compare as (*lhs == *rhs)</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">!=</span> <span class="identifier">o2</span> <span class="special">);</span> <span class="comment">//</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_less_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special"><</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> Expression <code class="computeroutput"><span class="special">*</span><span class="identifier">x</span> <span class="special"><</span> <span class="special">*</span><span class="identifier">y</span></code> shall be well-formed and its result
+ shall be convertible to <code class="computeroutput"><span class="keyword">bool</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">(!</span><span class="identifier">y</span><span class="special">)</span> <span class="special">?</span> <span class="keyword">false</span> <span class="special">:</span> <span class="special">(!</span><span class="identifier">x</span><span class="special">)</span> <span class="special">?</span> <span class="keyword">true</span> <span class="special">:</span> <span class="special">*</span><span class="identifier">x</span> <span class="special"><</span>
+ <span class="special">*</span><span class="identifier">y</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> This definition guarantees
+ that <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>
+ not containing a value is ordered as less than any <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> containing any value, and equivalent
+ to any other <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> not containing a value. Pointers
+ have shallow relational operators while <code class="computeroutput"><span class="identifier">optional</span></code>
+ has deep relational operators. Do not use <code class="computeroutput"><span class="keyword">operator</span><span class="special"><</span></code> directly in generic code which
+ expect to be given either an <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> or a pointer; use <a href="../../../../../../utility/OptionalPointee.html#less" target="_top"><code class="computeroutput"><span class="identifier">less_pointees</span><span class="special">()</span></code></a>
+ instead. <code class="computeroutput"><span class="identifier">T</span></code> need not
+ be <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a>. Only
+ single <code class="computeroutput"><span class="keyword">operator</span><span class="special"><</span></code>
+ is required. Other relational operations are defined in terms of this
+ one. If <code class="computeroutput"><span class="identifier">T</span></code>'s <code class="computeroutput"><span class="keyword">operator</span><span class="special"><</span></code>
+ satisfies the axioms of <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a> (transitivity,
+ antisymmetry and irreflexivity), <code class="computeroutput"><span class="identifier">optinal</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> is <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">oN</span><span class="special">,</span> <span class="identifier">oN_</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o0</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">0</span><span class="special">));</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o1</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">));</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN</span> <span class="special"><</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// Identity implies equivalence</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o1</span> <span class="special"><</span> <span class="identifier">o1</span><span class="special">)</span> <span class="special">);</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN</span> <span class="special"><</span> <span class="identifier">oN_</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// Two uninitialized are equivalent</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN_</span> <span class="special"><</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special"><</span> <span class="identifier">o0</span> <span class="special">);</span> <span class="comment">// Uninitialized is less than initialized</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o0</span> <span class="special"><</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special"><</span> <span class="identifier">o2</span> <span class="special">)</span> <span class="special">;</span> <span class="comment">// Two initialized compare as (*lhs < *rhs)</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o2</span> <span class="special"><</span> <span class="identifier">o1</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o2</span> <span class="special"><</span> <span class="identifier">o2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_not_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">!=</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
+ <span class="identifier">x</span> <span class="special">==</span>
+ <span class="identifier">y</span> <span class="special">);</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_greater_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">></span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">(</span>
+ <span class="identifier">y</span> <span class="special"><</span>
+ <span class="identifier">x</span> <span class="special">);</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_less_or_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special"><=</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
+ <span class="identifier">y</span> <span class="special"><</span>
+ <span class="identifier">x</span> <span class="special">);</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_greater_or_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">>=</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
+ <span class="identifier">x</span> <span class="special"><</span>
+ <span class="identifier">y</span> <span class="special">);</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_equal_optional_none"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">==</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">==</span> <span class="special">(</span>
+ <span class="identifier">none_t</span><span class="special">,</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">!</span><span class="identifier">x</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ need not meet requirements of <a href="http://www.sgi.com/tech/stl/EqualityComparable.html" target="_top"><code class="computeroutput"><span class="identifier">EqualityComparable</span></code></a>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_not_equal_optional_none"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">!=</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">!=</span> <span class="special">(</span>
+ <span class="identifier">none_t</span><span class="special">,</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
+ <span class="identifier">x</span> <span class="special">==</span>
+ <span class="identifier">y</span> <span class="special">);</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_swap_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">swap</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">y</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> Lvalues of type <code class="computeroutput"><span class="identifier">T</span></code> shall be swappable and <code class="computeroutput"><span class="identifier">T</span></code> shall be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>.
+ </li>
+<li class="listitem">
+<p class="simpara">
+ <span class="bold"><strong>Effects:</strong></span>
+ </p>
+<div class="informaltable"><table class="table">
+<colgroup>
+<col>
+<col>
+<col>
+</colgroup>
+<thead><tr></tr></thead>
+<tbody>
+<tr>
+<td>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ calls <code class="computeroutput"><span class="identifier">swap</span><span class="special">(*(*</span><span class="keyword">this</span><span class="special">),</span> <span class="special">*</span><span class="identifier">rhs</span><span class="special">)</span></code>
+ </p>
+ </td>
+<td>
+ <p>
+ initializes the contained value of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> as if direct-initializing
+ an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+ with the expression <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code>, followed by <code class="computeroutput"><span class="identifier">rhs</span><span class="special">.</span><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>,
+ <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ contains a value and <code class="computeroutput"><span class="identifier">rhs</span></code>
+ does not contain a value
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ does not contain a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ initializes the contained value of <code class="computeroutput"><span class="identifier">rhs</span></code>
+ as if direct-initializing an object of type <code class="computeroutput"><span class="identifier">T</span></code> with the expression
+ <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*(*</span><span class="keyword">this</span><span class="special">))</span></code>,
+ followed by <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value
+ and <code class="computeroutput"><span class="identifier">rhs</span></code> contains
+ a value
+ </p>
+ </td>
+<td>
+ <p>
+ no effect
+ </p>
+ </td>
+</tr>
+</tbody>
+</table></div>
+</li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> The states of <code class="computeroutput"><span class="identifier">x</span></code> and <code class="computeroutput"><span class="identifier">y</span></code>
+ interchanged.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> If both are initialized, whatever
+ <code class="computeroutput"><span class="identifier">swap</span><span class="special">(</span><span class="identifier">T</span><span class="special">&,</span><span class="identifier">T</span><span class="special">&)</span></code>
+ throws. If only one is initialized, whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code>
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">(</span><span class="number">12</span><span class="special">);</span>
+<span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">21</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def0</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def1</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">optX</span><span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">optY</span><span class="special">(</span><span class="identifier">y</span><span class="special">);</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">def1</span><span class="special">);</span> <span class="comment">// no-op</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">optX</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def0</span> <span class="special">==</span> <span class="identifier">x</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">optX</span> <span class="special">);</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">optX</span><span class="special">);</span> <span class="comment">// Get back to original values</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">optX</span><span class="special">,</span><span class="identifier">optY</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">optX</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">optY</span> <span class="special">==</span> <span class="identifier">x</span> <span class="special">);</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_swap_optional_reference"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">swap</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span> <span class="identifier">y</span>
+ <span class="special">)</span> <span class="keyword">noexcept</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="identifier">x</span></code>
+ refers to what <code class="computeroutput"><span class="identifier">y</span></code> refererred
+ to before the swap (if anything). <code class="computeroutput"><span class="identifier">y</span></code>
+ refers to whatever <code class="computeroutput"><span class="identifier">x</span></code>
+ referred to before the swap.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">(</span><span class="number">12</span><span class="special">);</span>
+<span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">21</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">opt0</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">optX</span> <span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">optY</span> <span class="special">(</span><span class="identifier">y</span><span class="special">);</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">optX</span><span class="special">,</span> <span class="identifier">optY</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">optX</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">y</span><span class="special">));</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">optY</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">x</span><span class="special">));</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">opt0</span><span class="special">,</span> <span class="identifier">optX</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt0</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">optX</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">opt0</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">y</span><span class="special">));</span>
+</pre>
+ [endsect]
+ </li>
+</ul></div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2016 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="header_optional_optional_refs.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header__boost_optional_hpp_.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
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+</html>
diff --git a/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics____free_functions.html b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics____free_functions.html
new file mode 100644
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+++ b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics____free_functions.html
@@ -0,0 +1,447 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Detailed Semantics -- Free Functions</title>
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+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
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+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics____free_functions"></a><a class="link" href="detailed_semantics____free_functions.html" title="Detailed Semantics -- Free Functions">Detailed
+ Semantics -- Free Functions</a>
+</h4></div></div></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_make_optional_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">make_optional</span><span class="special">(</span>
+ <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span></code> for the <span class="emphasis"><em>deduced</em></span>
+ type <code class="computeroutput"><span class="identifier">T</span></code> of <code class="computeroutput"><span class="identifier">v</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">void</span> <span class="identifier">foo</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">foo</span> <span class="special">(</span> <span class="identifier">make_optional</span><span class="special">(</span><span class="number">1</span><span class="special">+</span><span class="number">1</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> <span class="comment">// Creates an optional<int></span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_make_optional_bool_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="identifier">make_optional</span><span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span>
+ <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">condition</span><span class="special">,</span><span class="identifier">v</span><span class="special">)</span></code> for the <span class="emphasis"><em>deduced</em></span>
+ type <code class="computeroutput"><span class="identifier">T</span></code> of <code class="computeroutput"><span class="identifier">v</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">calculate_foo</span><span class="special">()</span>
+<span class="special">{</span>
+ <span class="keyword">double</span> <span class="identifier">val</span> <span class="special">=</span> <span class="identifier">compute_foo</span><span class="special">();</span>
+ <span class="keyword">return</span> <span class="identifier">make_optional</span><span class="special">(</span><span class="identifier">is_not_nan_and_finite</span><span class="special">(</span><span class="identifier">val</span><span class="special">),</span><span class="identifier">val</span><span class="special">);</span>
+<span class="special">}</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">v</span> <span class="special">=</span> <span class="identifier">calculate_foo</span><span class="special">();</span>
+<span class="keyword">if</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">v</span> <span class="special">)</span>
+ <span class="identifier">error</span><span class="special">(</span><span class="string">"foo wasn't computed"</span><span class="special">);</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">==</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ shall meet requirements of <a href="http://www.sgi.com/tech/stl/EqualityComparable.html" target="_top"><code class="computeroutput"><span class="identifier">EqualityComparable</span></code></a>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> If both <code class="computeroutput"><span class="identifier">x</span></code>
+ and <code class="computeroutput"><span class="identifier">y</span></code> are initialized,
+ <code class="computeroutput"><span class="special">(*</span><span class="identifier">x</span>
+ <span class="special">==</span> <span class="special">*</span><span class="identifier">y</span><span class="special">)</span></code>.
+ If only <code class="computeroutput"><span class="identifier">x</span></code> or <code class="computeroutput"><span class="identifier">y</span></code> is initialized, <code class="computeroutput"><span class="keyword">false</span></code>.
+ If both are uninitialized, <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> This definition guarantees
+ that <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>
+ not containing a value is compared unequal to any <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> containing any value, and equal
+ to any other <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> not containing a value. Pointers
+ have shallow relational operators while <code class="computeroutput"><span class="identifier">optional</span></code>
+ has deep relational operators. Do not use <code class="computeroutput"><span class="keyword">operator</span><span class="special">==</span></code> directly in generic code which expect
+ to be given either an <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> or a pointer; use <a href="../../../../../../utility/OptionalPointee.html#equal" target="_top"><code class="computeroutput"><span class="identifier">equal_pointees</span><span class="special">()</span></code></a>
+ instead
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">oN</span><span class="special">,</span> <span class="identifier">oN_</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o1</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">)),</span> <span class="identifier">o1_</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">));</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o2</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">));</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">==</span> <span class="identifier">oN</span> <span class="special">);</span> <span class="comment">// Identity implies equality</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">==</span> <span class="identifier">o1</span> <span class="special">);</span> <span class="comment">//</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">==</span> <span class="identifier">oN_</span> <span class="special">);</span> <span class="comment">// Both uninitialized compare equal</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">!=</span> <span class="identifier">o1</span> <span class="special">);</span> <span class="comment">// Initialized unequal to initialized.</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">==</span> <span class="identifier">o1_</span> <span class="special">);</span> <span class="comment">// Both initialized compare as (*lhs == *rhs)</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">!=</span> <span class="identifier">o2</span> <span class="special">);</span> <span class="comment">//</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_less_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special"><</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> Expression <code class="computeroutput"><span class="special">*</span><span class="identifier">x</span> <span class="special"><</span> <span class="special">*</span><span class="identifier">y</span></code> shall be well-formed and its result
+ shall be convertible to <code class="computeroutput"><span class="keyword">bool</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">(!</span><span class="identifier">y</span><span class="special">)</span> <span class="special">?</span> <span class="keyword">false</span> <span class="special">:</span> <span class="special">(!</span><span class="identifier">x</span><span class="special">)</span> <span class="special">?</span> <span class="keyword">true</span> <span class="special">:</span> <span class="special">*</span><span class="identifier">x</span> <span class="special"><</span>
+ <span class="special">*</span><span class="identifier">y</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> This definition guarantees
+ that <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>
+ not containing a value is ordered as less than any <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> containing any value, and equivalent
+ to any other <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> not containing a value. Pointers
+ have shallow relational operators while <code class="computeroutput"><span class="identifier">optional</span></code>
+ has deep relational operators. Do not use <code class="computeroutput"><span class="keyword">operator</span><span class="special"><</span></code> directly in generic code which
+ expect to be given either an <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> or a pointer; use <a href="../../../../../../utility/OptionalPointee.html#less" target="_top"><code class="computeroutput"><span class="identifier">less_pointees</span><span class="special">()</span></code></a>
+ instead. <code class="computeroutput"><span class="identifier">T</span></code> need not
+ be <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a>. Only
+ single <code class="computeroutput"><span class="keyword">operator</span><span class="special"><</span></code>
+ is required. Other relational operations are defined in terms of this
+ one. If <code class="computeroutput"><span class="identifier">T</span></code>'s <code class="computeroutput"><span class="keyword">operator</span><span class="special"><</span></code>
+ satisfies the axioms of <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a> (transitivity,
+ antisymmetry and irreflexivity), <code class="computeroutput"><span class="identifier">optinal</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> is <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">oN</span><span class="special">,</span> <span class="identifier">oN_</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o0</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">0</span><span class="special">));</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o1</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">));</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN</span> <span class="special"><</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// Identity implies equivalence</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o1</span> <span class="special"><</span> <span class="identifier">o1</span><span class="special">)</span> <span class="special">);</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN</span> <span class="special"><</span> <span class="identifier">oN_</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// Two uninitialized are equivalent</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN_</span> <span class="special"><</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special"><</span> <span class="identifier">o0</span> <span class="special">);</span> <span class="comment">// Uninitialized is less than initialized</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o0</span> <span class="special"><</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special"><</span> <span class="identifier">o2</span> <span class="special">)</span> <span class="special">;</span> <span class="comment">// Two initialized compare as (*lhs < *rhs)</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o2</span> <span class="special"><</span> <span class="identifier">o1</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o2</span> <span class="special"><</span> <span class="identifier">o2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_not_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">!=</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
+ <span class="identifier">x</span> <span class="special">==</span>
+ <span class="identifier">y</span> <span class="special">);</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_greater_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">></span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">(</span>
+ <span class="identifier">y</span> <span class="special"><</span>
+ <span class="identifier">x</span> <span class="special">);</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_less_or_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special"><=</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
+ <span class="identifier">y</span> <span class="special"><</span>
+ <span class="identifier">x</span> <span class="special">);</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_greater_or_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">>=</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
+ <span class="identifier">x</span> <span class="special"><</span>
+ <span class="identifier">y</span> <span class="special">);</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_equal_optional_none"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">==</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">==</span> <span class="special">(</span>
+ <span class="identifier">none_t</span><span class="special">,</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">!</span><span class="identifier">x</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ need not meet requirements of <a href="http://www.sgi.com/tech/stl/EqualityComparable.html" target="_top"><code class="computeroutput"><span class="identifier">EqualityComparable</span></code></a>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_not_equal_optional_none"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">!=</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">!=</span> <span class="special">(</span>
+ <span class="identifier">none_t</span><span class="special">,</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
+ <span class="identifier">x</span> <span class="special">==</span>
+ <span class="identifier">y</span> <span class="special">);</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_swap_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">swap</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">y</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> Lvalues of type <code class="computeroutput"><span class="identifier">T</span></code> shall be swappable and <code class="computeroutput"><span class="identifier">T</span></code> shall be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>.
+ </li>
+<li class="listitem">
+<p class="simpara">
+ <span class="bold"><strong>Effects:</strong></span>
+ </p>
+<div class="informaltable"><table class="table">
+<colgroup>
+<col>
+<col>
+<col>
+</colgroup>
+<thead><tr></tr></thead>
+<tbody>
+<tr>
+<td>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ calls <code class="computeroutput"><span class="identifier">swap</span><span class="special">(*(*</span><span class="keyword">this</span><span class="special">),</span> <span class="special">*</span><span class="identifier">rhs</span><span class="special">)</span></code>
+ </p>
+ </td>
+<td>
+ <p>
+ initializes the contained value of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> as if direct-initializing
+ an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+ with the expression <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code>, followed by <code class="computeroutput"><span class="identifier">rhs</span><span class="special">.</span><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>,
+ <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ contains a value and <code class="computeroutput"><span class="identifier">rhs</span></code>
+ does not contain a value
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ does not contain a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ initializes the contained value of <code class="computeroutput"><span class="identifier">rhs</span></code>
+ as if direct-initializing an object of type <code class="computeroutput"><span class="identifier">T</span></code> with the expression
+ <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*(*</span><span class="keyword">this</span><span class="special">))</span></code>,
+ followed by <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value
+ and <code class="computeroutput"><span class="identifier">rhs</span></code> contains
+ a value
+ </p>
+ </td>
+<td>
+ <p>
+ no effect
+ </p>
+ </td>
+</tr>
+</tbody>
+</table></div>
+</li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> The states of <code class="computeroutput"><span class="identifier">x</span></code> and <code class="computeroutput"><span class="identifier">y</span></code>
+ interchanged.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> If both are initialized, whatever
+ <code class="computeroutput"><span class="identifier">swap</span><span class="special">(</span><span class="identifier">T</span><span class="special">&,</span><span class="identifier">T</span><span class="special">&)</span></code>
+ throws. If only one is initialized, whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code>
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">(</span><span class="number">12</span><span class="special">);</span>
+<span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">21</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def0</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def1</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">optX</span><span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">optY</span><span class="special">(</span><span class="identifier">y</span><span class="special">);</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">def1</span><span class="special">);</span> <span class="comment">// no-op</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">optX</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def0</span> <span class="special">==</span> <span class="identifier">x</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">optX</span> <span class="special">);</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">optX</span><span class="special">);</span> <span class="comment">// Get back to original values</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">optX</span><span class="special">,</span><span class="identifier">optY</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">optX</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">optY</span> <span class="special">==</span> <span class="identifier">x</span> <span class="special">);</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_swap_optional_reference"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">swap</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span> <span class="identifier">y</span>
+ <span class="special">)</span> <span class="keyword">noexcept</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="identifier">x</span></code>
+ refers to what <code class="computeroutput"><span class="identifier">y</span></code> refererred
+ to before the swap (if anything). <code class="computeroutput"><span class="identifier">y</span></code>
+ refers to whatever <code class="computeroutput"><span class="identifier">x</span></code>
+ referred to before the swap.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">(</span><span class="number">12</span><span class="special">);</span>
+<span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">21</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">opt0</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">optX</span> <span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">optY</span> <span class="special">(</span><span class="identifier">y</span><span class="special">);</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">optX</span><span class="special">,</span> <span class="identifier">optY</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">optX</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">y</span><span class="special">));</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">optY</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">x</span><span class="special">));</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">opt0</span><span class="special">,</span> <span class="identifier">optX</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt0</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">optX</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">opt0</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">y</span><span class="special">));</span>
+</pre>
+ [endsect]
+ </li>
+</ul></div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2016 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="detailed_semantics____optional_references.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header__boost_optional_hpp_.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
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diff --git a/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics____optional_references.html b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics____optional_references.html
new file mode 100644
index 0000000..7eedfab
--- /dev/null
+++ b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics____optional_references.html
@@ -0,0 +1,57 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Detailed Semantics -- Optional References</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header <boost/optional/optional.hpp>">
+<link rel="prev" href="detailed_semantics____optional_values.html" title="Detailed Semantics -- Optional Values">
+<link rel="next" href="detailed_semantics____free_functions.html" title="Detailed Semantics -- Free Functions">
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+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
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+</tr></table>
+<hr>
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+<a accesskey="p" href="detailed_semantics____optional_values.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="detailed_semantics____free_functions.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics____optional_references"></a><a class="link" href="detailed_semantics____optional_references.html" title="Detailed Semantics -- Optional References">Detailed
+ Semantics -- Optional References</a>
+</h4></div></div></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_default_ctor"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><&>::</span><span class="identifier">optional</span><span class="special">()</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><&>::</span><span class="identifier">optional</span><span class="special">(</span><span class="identifier">none_t</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> refers to nothing.
+ </li></ul></div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2016 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="detailed_semantics____optional_values.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="detailed_semantics____free_functions.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>
diff --git a/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics____optional_values.html b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics____optional_values.html
new file mode 100644
index 0000000..5fd6391
--- /dev/null
+++ b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics____optional_values.html
@@ -0,0 +1,1983 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Detailed Semantics -- Optional Values</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header <boost/optional/optional.hpp>">
+<link rel="prev" href="header_optional_optional_refs.html" title="Optional References">
+<link rel="next" href="detailed_semantics____optional_references.html" title="Detailed Semantics -- Optional References">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="header_optional_optional_refs.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="detailed_semantics____optional_references.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics____optional_values"></a><a class="link" href="detailed_semantics____optional_values.html" title="Detailed Semantics -- Optional Values">Detailed
+ Semantics -- Optional Values</a>
+</h4></div></div></div>
+<div class="note"><table border="0" summary="Note">
+<tr>
+<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../../doc/src/images/note.png"></td>
+<th align="left">Note</th>
+</tr>
+<tr><td align="left" valign="top"><p>
+ The following section contains various <code class="computeroutput"><span class="identifier">assert</span><span class="special">()</span></code> which are used only to show the postconditions
+ as sample code. It is not implied that the type <code class="computeroutput"><span class="identifier">T</span></code>
+ must support each particular expression but that if the expression is
+ supported, the implied condition holds.
+ </p></td></tr>
+</table></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">()</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Default-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">uninitialized</span>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> T's default constructor <span class="underline">is not</span> called.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_none_t"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">none_t</span> <span class="special">)</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Constructs an <code class="computeroutput"><span class="identifier">optional</span></code> uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">uninitialized</span>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>'s
+ default constructor <span class="underline">is not</span> called.
+ The expression <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none</span></code>
+ denotes an instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none_t</span></code>
+ that can be used as the parameter.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">none</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">n</span><span class="special">(</span><span class="identifier">none</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">n</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_copy_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
+ is <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Directly-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
+ and its value is a <span class="emphasis"><em>copy</em></span> of <code class="computeroutput"><span class="identifier">v</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span></code> throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span></code> is called.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">);</span></code> in that case, this constructor
+ has no effect.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">ref</span> <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Directly-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
+ and its value is an instance of an internal type wrapping the reference
+ <code class="computeroutput"><span class="identifier">ref</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">T</span><span class="special">&</span> <span class="identifier">vref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">vref</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="special">++</span> <span class="identifier">v</span> <span class="special">;</span> <span class="comment">// mutate referee</span>
+<span class="identifier">assert</span> <span class="special">(*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span><span class="special">);</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_move_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">v</span>
+ <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
+ is <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Directly-Move-Constructs an
+ <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
+ and its value is move-constructed from <code class="computeroutput"><span class="identifier">v</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code>
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code>
+ is called.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">);</span></code>
+ in that case, the state of <code class="computeroutput"><span class="identifier">v</span></code>
+ is determined by exception safety guarantees for <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span><span class="special">&&)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v1</span><span class="special">,</span> <span class="identifier">v2</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">v1</span><span class="special">));</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v2</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">T</span><span class="special">&&</span>
+ <span class="identifier">ref</span> <span class="special">)</span>
+ <span class="special">=</span> <span class="keyword">delete</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> This constructor is deleted
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_bool_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span>
+ <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span>
+ <span class="special">::</span><span class="identifier">optional</span><span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span>
+ <span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">v</span> <span class="special">)</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ If condition is true, same as:
+ </li></ul></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span>
+ <span class="special">::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ otherwise, same as:
+ </li></ul></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">()</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span>
+ <span class="special">::</span><span class="identifier">optional</span><span class="special">()</span></code>
+ </p></blockquote></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">rhs</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_copy_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
+ is <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Copy-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> If rhs is initialized,
+ <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initialized and its value is a <span class="emphasis"><em>copy</em></span> of the
+ value of <code class="computeroutput"><span class="identifier">rhs</span></code>; else
+ <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span></code> throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If rhs is initialized, <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code>
+ is called.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">);</span></code> in that case, this constructor
+ has no effect.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">uninit</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">uninit</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init</span><span class="special">(</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span>
+ <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Copy-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initialized and its value is another reference to the same object
+ referenced by <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>;
+ else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> will refer to the same object
+ (they alias).
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">uninit</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">uninit</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span>
+
+<span class="identifier">T</span> <span class="identifier">v</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">ref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init</span><span class="special">(</span><span class="identifier">ref</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">v</span> <span class="special">=</span> <span class="number">3</span> <span class="special">;</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_move_constructor_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span> </code><span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span><span class="special">&&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span></code><span class="emphasis"><em>see below</em></span><code class="computeroutput"><span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
+ is <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Move-constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initialized and its value is move constructed from <code class="computeroutput"><span class="identifier">rhs</span></code>; else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code>
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> The expression inside <code class="computeroutput"><span class="keyword">noexcept</span></code> is equivalent to <code class="computeroutput"><span class="identifier">is_nothrow_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="special">&&</span>
+ <span class="special">)</span></code> is called.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">);</span></code>
+ in that case, <code class="computeroutput"><span class="identifier">rhs</span></code> remains
+ initialized and the value of <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by exception safety
+ of <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span><span class="special">&&)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">uninit</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">uninit</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">init</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">uniqye_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="keyword">new</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">init</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="keyword">nullptr</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init2</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">optional</span> <span class="special">&&</span>
+ <span class="identifier">rhs</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Move-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initialized and its value is another reference to the same object
+ referenced by <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>;
+ else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, both <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> will refer to the same object
+ (they alias).
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">uninit</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">uninit</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span>
+
+<span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">v</span><span class="special">(</span><span class="keyword">new</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">init</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">init</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="special">*</span><span class="identifier">v</span> <span class="special">=</span> <span class="number">3</span> <span class="special">;</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init2</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Copy-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initialized and its value is a <span class="emphasis"><em>copy</em></span> of the
+ value of rhs converted to type <code class="computeroutput"><span class="identifier">T</span></code>;
+ else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span></code> throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span></code> is called if <code class="computeroutput"><span class="identifier">rhs</span></code> is initialized, which requires
+ a valid conversion from <code class="computeroutput"><span class="identifier">U</span></code>
+ to <code class="computeroutput"><span class="identifier">T</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">);</span></code> in that case, this constructor
+ has no effect.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span><span class="number">123.4</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="number">123.4</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span><span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="number">123</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_move_constructor_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">>&&</span>
+ <span class="identifier">rhs</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Move-constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initialized and its value is move-constructed from <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>;
+ else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">)</span></code>
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">)</span></code>
+ is called if <code class="computeroutput"><span class="identifier">rhs</span></code> is
+ initialized, which requires a valid conversion from <code class="computeroutput"><span class="identifier">U</span></code>
+ to <code class="computeroutput"><span class="identifier">T</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">);</span></code>
+ in that case, <code class="computeroutput"><span class="identifier">rhs</span></code> remains
+ initialized and the value of <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by exception safety
+ guarantee of <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span>
+ <span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span><span class="number">123.4</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="number">123.4</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">x</span><span class="special">))</span> <span class="special">;</span>
+<span class="identifier">assert</span><span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="number">123</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_factory"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">InPlaceFactory</span><span class="special">></span>
+ <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">InPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">TypedInPlaceFactory</span><span class="special">></span>
+ <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">TypedInPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Constructs an <code class="computeroutput"><span class="identifier">optional</span></code> with a value of <code class="computeroutput"><span class="identifier">T</span></code> obtained from the factory.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
+ and its value is <span class="emphasis"><em>directly given</em></span> from the factory
+ <code class="computeroutput"><span class="identifier">f</span></code> (i.e., the value
+ <span class="underline">is not copied</span>).
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever the <code class="computeroutput"><span class="identifier">T</span></code> constructor called by the factory
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> See <a class="link" href="../../tutorial/in_place_factories.html" title="In-Place Factories">In-Place
+ Factories</a>
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during the call to the <code class="computeroutput"><span class="identifier">T</span></code>
+ constructor used by the factory; in that case, this constructor has
+ no effect.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">C</span> <span class="special">{</span> <span class="identifier">C</span> <span class="special">(</span> <span class="keyword">char</span><span class="special">,</span> <span class="keyword">double</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">)</span> <span class="special">;</span> <span class="special">}</span> <span class="special">;</span>
+
+<span class="identifier">C</span> <span class="identifier">v</span><span class="special">(</span><span class="char">'A'</span><span class="special">,</span><span class="number">123.4</span><span class="special">,</span><span class="string">"hello"</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">C</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span> <span class="identifier">in_place</span> <span class="special">(</span><span class="char">'A'</span><span class="special">,</span> <span class="number">123.4</span><span class="special">,</span> <span class="string">"hello"</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// InPlaceFactory used</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">C</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span> <span class="identifier">in_place</span><span class="special"><</span><span class="identifier">C</span><span class="special">>(</span><span class="char">'A'</span><span class="special">,</span> <span class="number">123.4</span><span class="special">,</span> <span class="string">"hello"</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// TypedInPlaceFactory used</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_equal_none_t"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">none_t</span>
+ <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized destroys its contained
+ value.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_equal_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">rhs</span> <span class="special">)</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Assigns the value <code class="computeroutput"><span class="identifier">rhs</span></code> to an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and its value is
+ a <span class="emphasis"><em>copy</em></span> of <code class="computeroutput"><span class="identifier">rhs</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span></code> or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&)</span></code>
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s assignment operator is used,
+ otherwise, its copy-constructor is used.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> In the event of
+ an exception, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified
+ as far as <code class="computeroutput"><span class="identifier">optional</span></code>
+ is concerned (it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s
+ <code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>).
+ If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s
+ <span class="emphasis"><em>copy constructor</em></span> fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">T</span> <span class="identifier">y</span><span class="special">;</span>
+<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">y</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">y</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> (Re)binds the wrapped reference.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and it references
+ the same object referenced by <code class="computeroutput"><span class="identifier">rhs</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, it is <span class="emphasis"><em>rebound</em></span>
+ to the new object. See <a class="link" href="../../tutorial/rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">here</a>
+ for details on this behavior.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
+<span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">ra</span><span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">rb</span> <span class="special">;</span> <span class="comment">// binds 'def' to 'b' through 'rb'</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">b</span> <span class="special">)</span> <span class="special">;</span>
+<span class="special">*</span><span class="identifier">def</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span> <span class="comment">// changes the value of 'b' to a copy of the value of 'a'</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">b</span> <span class="special">==</span> <span class="identifier">a</span> <span class="special">)</span> <span class="special">;</span>
+<span class="keyword">int</span> <span class="identifier">c</span> <span class="special">=</span> <span class="number">3</span><span class="special">;</span>
+<span class="keyword">int</span><span class="special">&</span> <span class="identifier">rc</span> <span class="special">=</span> <span class="identifier">c</span> <span class="special">;</span>
+<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">rc</span> <span class="special">;</span> <span class="comment">// REBINDS to 'c' through 'rc'</span>
+<span class="identifier">c</span> <span class="special">=</span> <span class="number">4</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="number">4</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_move_equal_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Moves the value <code class="computeroutput"><span class="identifier">rhs</span></code> to an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and its value is
+ moved from <code class="computeroutput"><span class="identifier">rhs</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code>
+ or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span> <span class="special">&&)</span></code>
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s move-assignment operator is used,
+ otherwise, its move-constructor is used.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> In the event of
+ an exception, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified
+ as far as <code class="computeroutput"><span class="identifier">optional</span></code>
+ is concerned (it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s
+ <code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>).
+ If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s
+ <span class="emphasis"><em>move constructor</em></span> fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">T</span> <span class="identifier">y1</span><span class="special">,</span> <span class="identifier">y2</span><span class="special">,</span> <span class="identifier">yR</span><span class="special">;</span>
+<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">y1</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">yR</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">y2</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">yR</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="special">=</span>
+ <span class="keyword">delete</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> This assignment operator is
+ deleted.
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_equal_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">rhs</span> <span class="special">)</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ is <a href="../../../../../../utility/CopyConstructible.html" target="_top"><code class="computeroutput"><span class="identifier">CopyConstructible</span></code></a> and <code class="computeroutput"><span class="identifier">CopyAssignable</span></code>.
+ </li>
+<li class="listitem">
+<p class="simpara">
+ <span class="bold"><strong>Effects:</strong></span>
+ </p>
+<div class="informaltable"><table class="table">
+<colgroup>
+<col>
+<col>
+<col>
+</colgroup>
+<thead><tr></tr></thead>
+<tbody>
+<tr>
+<td>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ assigns <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
+ to the contained value
+ </p>
+ </td>
+<td>
+ <p>
+ initializes the contained value as if direct-initializing
+ an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+ with <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ does not contain a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>
+ </p>
+ </td>
+<td>
+ <p>
+ no effect
+ </p>
+ </td>
+</tr>
+</tbody>
+</table></div>
+</li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>;
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> If any exception
+ is thrown, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">rhs</span></code>
+ remains unchanged. If an exception is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s copy constructor, no effect.
+ If an exception is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s
+ copy assignment, the state of its contained value is as defined by
+ the exception safety guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s
+ copy assignment.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
+
+<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span>
+<span class="comment">// previous value (copy of 'v') destroyed from within 'opt'.</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span>
+ <span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> (Re)binds thee wrapped reference.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initialized and it references the same object referenced by <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>;
+ otherwise, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is uninitialized (and references no object).
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized and so is <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>,
+ <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is <span class="emphasis"><em>rebound</em></span> to the new object. See <a class="link" href="../../tutorial/rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">here</a>
+ for details on this behavior.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
+<span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">ora</span><span class="special">(</span><span class="identifier">ra</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">orb</span><span class="special">(</span><span class="identifier">rb</span><span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">orb</span> <span class="special">;</span> <span class="comment">// binds 'def' to 'b' through 'rb' wrapped within 'orb'</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">b</span> <span class="special">)</span> <span class="special">;</span>
+<span class="special">*</span><span class="identifier">def</span> <span class="special">=</span> <span class="identifier">ora</span> <span class="special">;</span> <span class="comment">// changes the value of 'b' to a copy of the value of 'a'</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">b</span> <span class="special">==</span> <span class="identifier">a</span> <span class="special">)</span> <span class="special">;</span>
+<span class="keyword">int</span> <span class="identifier">c</span> <span class="special">=</span> <span class="number">3</span><span class="special">;</span>
+<span class="keyword">int</span><span class="special">&</span> <span class="identifier">rc</span> <span class="special">=</span> <span class="identifier">c</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">orc</span><span class="special">(</span><span class="identifier">rc</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">ora</span> <span class="special">=</span> <span class="identifier">orc</span> <span class="special">;</span> <span class="comment">// REBINDS ora to 'c' through 'rc'</span>
+<span class="identifier">c</span> <span class="special">=</span> <span class="number">4</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">ora</span> <span class="special">==</span> <span class="number">4</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_move_equal_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span></code><span class="emphasis"><em>see below</em></span><code class="computeroutput"><span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ is <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>
+ and <code class="computeroutput"><span class="identifier">MoveAssignable</span></code>.
+ </li>
+<li class="listitem">
+<p class="simpara">
+ <span class="bold"><strong>Effects:</strong></span>
+ </p>
+<div class="informaltable"><table class="table">
+<colgroup>
+<col>
+<col>
+<col>
+</colgroup>
+<thead><tr></tr></thead>
+<tbody>
+<tr>
+<td>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ assigns <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code> to the contained value
+ </p>
+ </td>
+<td>
+ <p>
+ initializes the contained value as if direct-initializing
+ an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+ with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ does not contain a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>
+ </p>
+ </td>
+<td>
+ <p>
+ no effect
+ </p>
+ </td>
+</tr>
+</tbody>
+</table></div>
+</li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>;
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> The expression inside <code class="computeroutput"><span class="keyword">noexcept</span></code> is equivalent to <code class="computeroutput"><span class="identifier">is_nothrow_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span> <span class="special">&&</span>
+ <span class="identifier">is_nothrow_move_assignable</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> If any exception
+ is thrown, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">rhs</span></code>
+ remains unchanged. If an exception is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s move constructor, the state of
+ <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
+ is determined by the exception safety guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s
+ move constructor. If an exception is thrown during the call to T's
+ move-assignment, the state of <code class="computeroutput"><span class="special">**</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by the exception
+ safety guarantee of T's move assignment.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
+
+<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span>
+ <span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Same as <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">rhs</span> <span class="special">)</span></code>.
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_equal_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+<p class="simpara">
+ <span class="bold"><strong>Effect:</strong></span>
+ </p>
+<div class="informaltable"><table class="table">
+<colgroup>
+<col>
+<col>
+<col>
+</colgroup>
+<thead><tr></tr></thead>
+<tbody>
+<tr>
+<td>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ assigns <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
+ to the contained value
+ </p>
+ </td>
+<td>
+ <p>
+ initializes the contained value as if direct-initializing
+ an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+ with <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ does not contain a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>
+ </p>
+ </td>
+<td>
+ <p>
+ no effect
+ </p>
+ </td>
+</tr>
+</tbody>
+</table></div>
+</li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> If any exception
+ is thrown, the result of the expression <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code> remains unchanged. If an exception
+ is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s
+ constructor, no effect. If an exception is thrown during the call to
+ <code class="computeroutput"><span class="identifier">T</span></code>'s assignment, the
+ state of its contained value is as defined by the exception safety
+ guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s copy
+ assignment.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt0</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">opt1</span><span class="special">;</span>
+
+<span class="identifier">opt1</span> <span class="special">=</span> <span class="identifier">opt0</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt1</span> <span class="special">==</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_move_equal_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">>&&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+<p class="simpara">
+ <span class="bold"><strong>Effect:</strong></span>
+ </p>
+<div class="informaltable"><table class="table">
+<colgroup>
+<col>
+<col>
+<col>
+</colgroup>
+<thead><tr></tr></thead>
+<tbody>
+<tr>
+<td>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ assigns <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code> to the contained value
+ </p>
+ </td>
+<td>
+ <p>
+ initializes the contained value as if direct-initializing
+ an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+ with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ does not contain a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>
+ </p>
+ </td>
+<td>
+ <p>
+ no effect
+ </p>
+ </td>
+</tr>
+</tbody>
+</table></div>
+</li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> If any exception
+ is thrown, the result of the expression <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code> remains unchanged. If an exception
+ is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s
+ constructor, no effect. If an exception is thrown during the call to
+ <code class="computeroutput"><span class="identifier">T</span></code>'s assignment, the
+ state of its contained value is as defined by the exception safety
+ guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s copy
+ assignment.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt0</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">opt1</span><span class="special">;</span>
+
+<span class="identifier">opt1</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">opt0</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt0</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt1</span> <span class="special">)</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt1</span> <span class="special">==</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_emplace"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">></span>
+ <span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">emplace</span><span class="special">(</span>
+ <span class="identifier">Args</span><span class="special">...&&</span>
+ <span class="identifier">args</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> The compiler supports rvalue
+ references and variadic templates.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized calls <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span> <span class="special">=</span> <span class="identifier">none</span></code>.
+ Then initializes in-place the contained value as if direct-initializing
+ an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+ with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">Args</span><span class="special">>(</span><span class="identifier">args</span><span class="special">)...</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever the selected <code class="computeroutput"><span class="identifier">T</span></code>'s constructor throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> If an exception
+ is thrown during the initialization of <code class="computeroutput"><span class="identifier">T</span></code>,
+ <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is <span class="emphasis"><em>uninitialized</em></span>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ need not be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>
+ or <code class="computeroutput"><span class="identifier">MoveAssignable</span></code>.
+ On compilers that do not support variadic templates, the signature
+ falls back to two overloads:<code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span>
+ <span class="identifier">Arg</span><span class="special">></span>
+ <span class="keyword">void</span> <span class="identifier">emplace</span><span class="special">(</span><span class="identifier">Arg</span><span class="special">&&</span> <span class="identifier">arg</span><span class="special">)</span></code> and <code class="computeroutput"><span class="keyword">void</span>
+ <span class="identifier">emplace</span><span class="special">()</span></code>.
+ On compilers that do not support rvalue references, the signature falls
+ back to three overloads: taking <code class="computeroutput"><span class="keyword">const</span></code>
+ and non-<code class="computeroutput"><span class="keyword">const</span></code> lvalue reference,
+ and third with empty function argument list.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">const</span> <span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">;</span>
+<span class="identifier">opt</span><span class="special">.</span><span class="identifier">emplace</span><span class="special">(</span><span class="number">0</span><span class="special">);</span> <span class="comment">// create in-place using ctor T(int)</span>
+<span class="identifier">opt</span><span class="special">.</span><span class="identifier">emplace</span><span class="special">();</span> <span class="comment">// destroy previous and default-construct another T</span>
+<span class="identifier">opt</span><span class="special">.</span><span class="identifier">emplace</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> <span class="comment">// destroy and copy-construct in-place (no assignment called)</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_equal_factory"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">InPlaceFactory</span><span class="special">></span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">InPlaceFactory</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">f</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">TypedInPlaceFactory</span><span class="special">></span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">TypedInPlaceFactory</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">f</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Assigns an <code class="computeroutput"><span class="identifier">optional</span></code>
+ with a value of <code class="computeroutput"><span class="identifier">T</span></code> obtained
+ from the factory.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
+ and its value is <span class="emphasis"><em>directly given</em></span> from the factory
+ <code class="computeroutput"><span class="identifier">f</span></code> (i.e., the value
+ <span class="underline">is not copied</span>).
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever the <code class="computeroutput"><span class="identifier">T</span></code> constructor called by the factory
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> See <a class="link" href="../../tutorial/in_place_factories.html" title="In-Place Factories">In-Place
+ Factories</a>
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during the call to the <code class="computeroutput"><span class="identifier">T</span></code>
+ constructor used by the factory; in that case, the <code class="computeroutput"><span class="identifier">optional</span></code>
+ object will be reset to be <span class="emphasis"><em>uninitialized</em></span>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_reset_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">reset</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Deprecated:</strong></span> same as <code class="computeroutput"><span class="keyword">operator</span><span class="special">=</span>
+ <span class="special">(</span> <span class="identifier">T</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">v</span><span class="special">)</span>
+ <span class="special">;</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_reset"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reset</span><span class="special">()</span> <span class="keyword">noexcept</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Deprecated:</strong></span> Same as <code class="computeroutput"><span class="keyword">operator</span><span class="special">=(</span>
+ <span class="identifier">none_t</span> <span class="special">);</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_get"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get</span><span class="special">()</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">get</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span>
+ <span class="special">&)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> A reference to the contained
+ value
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The requirement is asserted
+ via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">get</span><span class="special">()</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">get</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="special">&)</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <span class="underline">The</span>
+ reference contained.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The requirement is asserted
+ via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_asterisk"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">*()</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">*()</span> <span class="special">&;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> A reference to the contained
+ value
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The requirement is asserted
+ via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
+ On compilers that do not support ref-qualifiers on member functions
+ these two overloads are replaced with the classical two: a <code class="computeroutput"><span class="keyword">const</span></code> and non-<code class="computeroutput"><span class="keyword">const</span></code>
+ member functions.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span>
+<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">u</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">opt</span><span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">u</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">T</span> <span class="identifier">w</span> <span class="special">;</span>
+<span class="special">*</span><span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">w</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">w</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_asterisk_move"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span><span class="special">*()</span> <span class="special">&&;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">val</span><span class="special">);</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The requirement is asserted
+ via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
+ On compilers that do not support ref-qualifiers on member functions
+ this overload is not present.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">*()</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">*()</span>
+ <span class="special">&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">*()</span>
+ <span class="special">&&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <span class="underline">The</span>
+ reference contained.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The requirement is asserted
+ via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
+ On compilers that do not support ref-qualifiers on member functions
+ these three overloads are replaced with the classical two: a <code class="computeroutput"><span class="keyword">const</span></code> and non-<code class="computeroutput"><span class="keyword">const</span></code>
+ member functions.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&</span> <span class="identifier">vref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">vref</span> <span class="special">);</span>
+<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">vref2</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">opt</span><span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">vref2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="special">++</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span><span class="special">()</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span><span class="special">()</span> <span class="special">&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">?</span> <span class="special">*</span><span class="identifier">val</span> <span class="special">:</span> <span class="keyword">throw</span> <span class="identifier">bad_optional_access</span><span class="special">();</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ ref-qualifiers on member functions these two overloads are replaced
+ with the classical two: a <code class="computeroutput"><span class="keyword">const</span></code>
+ and non-<code class="computeroutput"><span class="keyword">const</span></code> member functions.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o0</span><span class="special">,</span> <span class="identifier">o1</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span><span class="special">.</span><span class="identifier">value</span><span class="special">()</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">);</span>
+
+<span class="keyword">try</span> <span class="special">{</span>
+ <span class="identifier">o0</span><span class="special">.</span><span class="identifier">value</span><span class="special">();</span> <span class="comment">// throws</span>
+ <span class="identifier">assert</span> <span class="special">(</span> <span class="keyword">false</span> <span class="special">);</span>
+<span class="special">}</span>
+<span class="keyword">catch</span><span class="special">(</span><span class="identifier">bad_optional_access</span><span class="special">&)</span> <span class="special">{</span>
+ <span class="identifier">assert</span> <span class="special">(</span> <span class="keyword">true</span> <span class="special">);</span>
+<span class="special">}</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_value_move"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span><span class="special">()</span> <span class="special">&&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">?</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">val</span><span class="special">)</span> <span class="special">:</span> <span class="keyword">throw</span> <span class="identifier">bad_optional_access</span><span class="special">();</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ ref-qualifiers on member functions this overload is not present.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_value_or"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or</span><span class="special">(</span><span class="identifier">U</span> <span class="special">&&</span>
+ <span class="identifier">v</span><span class="special">)</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">if</span> <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="special">**</span><span class="keyword">this</span><span class="special">;</span> <span class="keyword">else</span> <span class="keyword">return</span>
+ <span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">);</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> If <code class="computeroutput"><span class="identifier">T</span></code>
+ is not <a href="../../../../../../utility/CopyConstructible.html" target="_top"><code class="computeroutput"><span class="identifier">CopyConstructible</span></code></a> or <code class="computeroutput"><span class="identifier">U</span> <span class="special">&&</span></code>
+ is not convertible to <code class="computeroutput"><span class="identifier">T</span></code>,
+ the program is ill-formed.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ ref-qualifiers on member functions this overload is replaced with the
+ <code class="computeroutput"><span class="keyword">const</span></code>-qualified member
+ function. On compilers without rvalue reference support the type of
+ <code class="computeroutput"><span class="identifier">v</span></code> becomes <code class="computeroutput"><span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span></code>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_value_or_move"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or</span><span class="special">(</span><span class="identifier">U</span> <span class="special">&&</span>
+ <span class="identifier">v</span><span class="special">)</span>
+ <span class="special">&&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">if</span> <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(**</span><span class="keyword">this</span><span class="special">);</span> <span class="keyword">else</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">);</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> If <code class="computeroutput"><span class="identifier">T</span></code>
+ is not <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>
+ or <code class="computeroutput"><span class="identifier">U</span> <span class="special">&&</span></code>
+ is not convertible to <code class="computeroutput"><span class="identifier">T</span></code>,
+ the program is ill-formed.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ ref-qualifiers on member functions this overload is not present.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_value_or_call"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">F</span> <span class="identifier">f</span><span class="special">)</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ is <a href="../../../../../../utility/CopyConstructible.html" target="_top"><code class="computeroutput"><span class="identifier">CopyConstructible</span></code></a> and <code class="computeroutput"><span class="identifier">F</span></code> models a <a href="http://www.sgi.com/tech/stl/Generator.html" target="_top"><code class="computeroutput"><span class="identifier">Generator</span></code></a> whose result type
+ is convertible to <code class="computeroutput"><span class="identifier">T</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> <code class="computeroutput"><span class="keyword">if</span>
+ <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="special">**</span><span class="keyword">this</span><span class="special">;</span> <span class="keyword">else</span> <span class="keyword">return</span> <span class="identifier">f</span><span class="special">();</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ ref-qualifiers on member functions this overload is replaced with the
+ <code class="computeroutput"><span class="keyword">const</span></code>-qualified member
+ function.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">complain_and_0</span><span class="special">()</span>
+<span class="special">{</span>
+ <span class="identifier">clog</span> <span class="special"><<</span> <span class="string">"no value returned, using default"</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span>
+ <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
+<span class="special">}</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">o1</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">oN</span> <span class="special">=</span> <span class="identifier">none</span><span class="special">;</span>
+
+<span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="identifier">o1</span><span class="special">.</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">complain_and_0</span><span class="special">);</span> <span class="comment">// fun not called</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">i</span> <span class="special">==</span> <span class="number">1</span><span class="special">);</span>
+
+<span class="keyword">int</span> <span class="identifier">j</span> <span class="special">=</span> <span class="identifier">oN</span><span class="special">.</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">complain_and_0</span><span class="special">);</span> <span class="comment">// fun called</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">i</span> <span class="special">==</span> <span class="number">0</span><span class="special">);</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_value_or_call_move"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">F</span> <span class="identifier">f</span><span class="special">)</span> <span class="special">&&</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ is <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>
+ and <code class="computeroutput"><span class="identifier">F</span></code> models a <a href="http://www.sgi.com/tech/stl/Generator.html" target="_top"><code class="computeroutput"><span class="identifier">Generator</span></code></a>
+ whose result type is convertible to <code class="computeroutput"><span class="identifier">T</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> <code class="computeroutput"><span class="keyword">if</span>
+ <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(**</span><span class="keyword">this</span><span class="special">);</span> <span class="keyword">else</span> <span class="keyword">return</span>
+ <span class="identifier">f</span><span class="special">();</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ ref-qualifiers on member functions this overload is not present.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_get_value_or_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_value_or</span><span class="special">(</span>
+ <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="keyword">default</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_value_or</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&</span> <span class="keyword">default</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">get_optional_value_or</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">o</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="keyword">default</span> <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get_optional_value_or</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>&</span>
+ <span class="identifier">o</span><span class="special">,</span>
+ <span class="identifier">T</span><span class="special">&</span>
+ <span class="keyword">default</span> <span class="special">)</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Deprecated:</strong></span> Use <code class="computeroutput"><span class="identifier">value_or</span><span class="special">()</span></code> instead.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> A reference to the contained
+ value, if any, or <code class="computeroutput"><span class="keyword">default</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">,</span> <span class="identifier">z</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span><span class="special">;</span>
+<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">=</span> <span class="identifier">def</span><span class="special">.</span><span class="identifier">get_value_or</span><span class="special">(</span><span class="identifier">z</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">y</span> <span class="special">==</span> <span class="identifier">z</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span>
+<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">u</span> <span class="special">=</span> <span class="identifier">get_optional_value_or</span><span class="special">(</span><span class="identifier">opt</span><span class="special">,</span><span class="identifier">z</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">u</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">u</span> <span class="special">!=</span> <span class="identifier">z</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_get_ptr"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_ptr</span><span class="special">()</span>
+ <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">*</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span>
+ <span class="keyword">const</span><span class="special">*</span>
+ <span class="identifier">get_pointer</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">get_pointer</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">></span>
+ <span class="special">&)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized, a pointer to the
+ contained value; else <code class="computeroutput"><span class="number">0</span></code>
+ (<span class="emphasis"><em>null</em></span>).
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The contained value is permanently
+ stored within <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>,
+ so you should not hold nor delete this pointer
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span> <span class="identifier">copt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">T</span><span class="special">*</span> <span class="identifier">p</span> <span class="special">=</span> <span class="identifier">opt</span><span class="special">.</span><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">;</span>
+<span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">cp</span> <span class="special">=</span> <span class="identifier">copt</span><span class="special">.</span><span class="identifier">get_ptr</span><span class="special">();</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">p</span> <span class="special">==</span> <span class="identifier">get_pointer</span><span class="special">(</span><span class="identifier">opt</span><span class="special">)</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">cp</span> <span class="special">==</span> <span class="identifier">get_pointer</span><span class="special">(</span><span class="identifier">copt</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_arrow"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code>
+ <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span> <span class="special">->()</span>
+ <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">*</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span></code> <span class="emphasis"><em>(not a ref)</em></span><code class="computeroutput"><span class="special">>::</span><span class="keyword">operator</span>
+ <span class="special">->()</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> A pointer to the contained
+ value.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The requirement is asserted
+ via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">X</span> <span class="special">{</span> <span class="keyword">int</span> <span class="identifier">mdata</span> <span class="special">;</span> <span class="special">}</span> <span class="special">;</span>
+<span class="identifier">X</span> <span class="identifier">x</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">X</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
+<span class="identifier">opt</span><span class="special">-></span><span class="identifier">mdata</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_bool"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span>
+ <span class="keyword">bool</span><span class="special">()</span>
+ <span class="keyword">const</span> <span class="keyword">noexcept</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">!=</span> <span class="number">0</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ explicit conversion operators this falls back to safe-bool idiom.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def</span> <span class="special">==</span> <span class="number">0</span> <span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">!=</span> <span class="number">0</span> <span class="special">);</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_not"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">noexcept</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized, <code class="computeroutput"><span class="keyword">true</span></code>; else <code class="computeroutput"><span class="keyword">false</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> This operator is provided for
+ those compilers which can't use the <span class="emphasis"><em>unspecified-bool-type
+ operator</em></span> in certain boolean contexts.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">opt</span> <span class="special">);</span>
+<span class="special">*</span><span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">some_T</span> <span class="special">;</span>
+
+<span class="comment">// Notice the "double-bang" idiom here.</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!!</span><span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_is_initialized"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_initialized</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Deprecated:</strong></span> Same as <code class="computeroutput"><span class="keyword">explicit</span> <span class="keyword">operator</span>
+ <span class="keyword">bool</span> <span class="special">()</span>
+ <span class="special">;</span></code>
+ </li></ul></div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2016 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="header_optional_optional_refs.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="detailed_semantics____optional_references.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>
diff --git a/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html
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+++ b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___free_functions.html
@@ -0,0 +1,521 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Detailed Semantics - Free Functions</title>
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+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
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+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics___free_functions"></a><a class="link" href="detailed_semantics___free_functions.html" title="Detailed Semantics - Free Functions">Detailed
+ Semantics - Free Functions</a>
+</h4></div></div></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_make_optional_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">make_optional</span><span class="special">(</span>
+ <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span></code> for the <span class="emphasis"><em>deduced</em></span>
+ type <code class="computeroutput"><span class="identifier">T</span></code> of <code class="computeroutput"><span class="identifier">v</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">void</span> <span class="identifier">foo</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">foo</span> <span class="special">(</span> <span class="identifier">make_optional</span><span class="special">(</span><span class="number">1</span><span class="special">+</span><span class="number">1</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span> <span class="comment">// Creates an optional<int></span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_make_optional_rvalue"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">decay_t</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span>
+ <span class="identifier">make_optional</span><span class="special">(</span>
+ <span class="identifier">T</span> <span class="special">&&</span>
+ <span class="identifier">v</span> <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">decay_t</span><span class="special"><</span><span class="identifier">T</span><span class="special">>>(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">v</span><span class="special">))</span></code> for the <span class="emphasis"><em>deduced</em></span>
+ type <code class="computeroutput"><span class="identifier">T</span></code> of <code class="computeroutput"><span class="identifier">v</span></code>.
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_make_optional_bool_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">make_optional</span><span class="special">(</span>
+ <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="identifier">condition</span><span class="special">,</span> <span class="identifier">v</span><span class="special">)</span></code> for the <span class="emphasis"><em>deduced</em></span>
+ type <code class="computeroutput"><span class="identifier">T</span></code> of <code class="computeroutput"><span class="identifier">v</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">calculate_foo</span><span class="special">()</span>
+<span class="special">{</span>
+ <span class="keyword">double</span> <span class="identifier">val</span> <span class="special">=</span> <span class="identifier">compute_foo</span><span class="special">();</span>
+ <span class="keyword">return</span> <span class="identifier">make_optional</span><span class="special">(</span><span class="identifier">is_not_nan_and_finite</span><span class="special">(</span><span class="identifier">val</span><span class="special">),</span><span class="identifier">val</span><span class="special">);</span>
+<span class="special">}</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">v</span> <span class="special">=</span> <span class="identifier">calculate_foo</span><span class="special">();</span>
+<span class="keyword">if</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">v</span> <span class="special">)</span>
+ <span class="identifier">error</span><span class="special">(</span><span class="string">"foo wasn't computed"</span><span class="special">);</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_make_optional_bool_rvalue"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">decay_t</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span>
+ <span class="identifier">make_optional</span><span class="special">(</span>
+ <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">T</span> <span class="special">&&</span> <span class="identifier">v</span>
+ <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">decay_t</span><span class="special"><</span><span class="identifier">T</span><span class="special">>>(</span><span class="identifier">condition</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">v</span><span class="special">))</span></code> for the <span class="emphasis"><em>deduced</em></span>
+ type <code class="computeroutput"><span class="identifier">T</span></code> of <code class="computeroutput"><span class="identifier">v</span></code>.
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">==</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ shall meet requirements of <a href="http://www.sgi.com/tech/stl/EqualityComparable.html" target="_top"><code class="computeroutput"><span class="identifier">EqualityComparable</span></code></a>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> If both <code class="computeroutput"><span class="identifier">x</span></code>
+ and <code class="computeroutput"><span class="identifier">y</span></code> are initialized,
+ <code class="computeroutput"><span class="special">(*</span><span class="identifier">x</span>
+ <span class="special">==</span> <span class="special">*</span><span class="identifier">y</span><span class="special">)</span></code>.
+ If only <code class="computeroutput"><span class="identifier">x</span></code> or <code class="computeroutput"><span class="identifier">y</span></code> is initialized, <code class="computeroutput"><span class="keyword">false</span></code>.
+ If both are uninitialized, <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> This definition guarantees
+ that <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>
+ not containing a value is compared unequal to any <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> containing any value, and equal
+ to any other <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> not containing a value. Pointers
+ have shallow relational operators while <code class="computeroutput"><span class="identifier">optional</span></code>
+ has deep relational operators. Do not use <code class="computeroutput"><span class="keyword">operator</span><span class="special">==</span></code> directly in generic code which expect
+ to be given either an <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> or a pointer; use <a href="../../../../../../utility/OptionalPointee.html#equal" target="_top"><code class="computeroutput"><span class="identifier">equal_pointees</span><span class="special">()</span></code></a>
+ instead
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">oN</span><span class="special">,</span> <span class="identifier">oN_</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o1</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">)),</span> <span class="identifier">o1_</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">));</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o2</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">));</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">==</span> <span class="identifier">oN</span> <span class="special">);</span> <span class="comment">// Identity implies equality</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">==</span> <span class="identifier">o1</span> <span class="special">);</span> <span class="comment">//</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">==</span> <span class="identifier">oN_</span> <span class="special">);</span> <span class="comment">// Both uninitialized compare equal</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special">!=</span> <span class="identifier">o1</span> <span class="special">);</span> <span class="comment">// Initialized unequal to initialized.</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">==</span> <span class="identifier">o1_</span> <span class="special">);</span> <span class="comment">// Both initialized compare as (*lhs == *rhs)</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special">!=</span> <span class="identifier">o2</span> <span class="special">);</span> <span class="comment">//</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_less_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special"><</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> Expression <code class="computeroutput"><span class="special">*</span><span class="identifier">x</span> <span class="special"><</span> <span class="special">*</span><span class="identifier">y</span></code> shall be well-formed and its result
+ shall be convertible to <code class="computeroutput"><span class="keyword">bool</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">(!</span><span class="identifier">y</span><span class="special">)</span> <span class="special">?</span> <span class="keyword">false</span> <span class="special">:</span> <span class="special">(!</span><span class="identifier">x</span><span class="special">)</span> <span class="special">?</span> <span class="keyword">true</span> <span class="special">:</span> <span class="special">*</span><span class="identifier">x</span> <span class="special"><</span>
+ <span class="special">*</span><span class="identifier">y</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> This definition guarantees
+ that <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>
+ not containing a value is ordered as less than any <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> containing any value, and equivalent
+ to any other <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> not containing a value. Pointers
+ have shallow relational operators while <code class="computeroutput"><span class="identifier">optional</span></code>
+ has deep relational operators. Do not use <code class="computeroutput"><span class="keyword">operator</span><span class="special"><</span></code> directly in generic code which
+ expect to be given either an <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> or a pointer; use <a href="../../../../../../utility/OptionalPointee.html#less" target="_top"><code class="computeroutput"><span class="identifier">less_pointees</span><span class="special">()</span></code></a>
+ instead. <code class="computeroutput"><span class="identifier">T</span></code> need not
+ be <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a>. Only
+ single <code class="computeroutput"><span class="keyword">operator</span><span class="special"><</span></code>
+ is required. Other relational operations are defined in terms of this
+ one. If <code class="computeroutput"><span class="identifier">T</span></code>'s <code class="computeroutput"><span class="keyword">operator</span><span class="special"><</span></code>
+ satisfies the axioms of <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a> (transitivity,
+ antisymmetry and irreflexivity), <code class="computeroutput"><span class="identifier">optinal</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> is <a href="http://www.sgi.com/tech/stl/LessThanComparable.html" target="_top"><code class="computeroutput"><span class="identifier">LessThanComparable</span></code></a>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">oN</span><span class="special">,</span> <span class="identifier">oN_</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o0</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">0</span><span class="special">));</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o1</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">1</span><span class="special">));</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN</span> <span class="special"><</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// Identity implies equivalence</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o1</span> <span class="special"><</span> <span class="identifier">o1</span><span class="special">)</span> <span class="special">);</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN</span> <span class="special"><</span> <span class="identifier">oN_</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// Two uninitialized are equivalent</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">oN_</span> <span class="special"><</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">oN</span> <span class="special"><</span> <span class="identifier">o0</span> <span class="special">);</span> <span class="comment">// Uninitialized is less than initialized</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o0</span> <span class="special"><</span> <span class="identifier">oN</span><span class="special">)</span> <span class="special">);</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span> <span class="special"><</span> <span class="identifier">o2</span> <span class="special">)</span> <span class="special">;</span> <span class="comment">// Two initialized compare as (*lhs < *rhs)</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o2</span> <span class="special"><</span> <span class="identifier">o1</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!(</span><span class="identifier">o2</span> <span class="special"><</span> <span class="identifier">o2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_not_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">!=</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
+ <span class="identifier">x</span> <span class="special">==</span>
+ <span class="identifier">y</span> <span class="special">);</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_greater_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">></span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">(</span>
+ <span class="identifier">y</span> <span class="special"><</span>
+ <span class="identifier">x</span> <span class="special">);</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_less_or_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special"><=</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
+ <span class="identifier">y</span> <span class="special"><</span>
+ <span class="identifier">x</span> <span class="special">);</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_greater_or_equal_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">>=</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="special">!(</span>
+ <span class="identifier">x</span> <span class="special"><</span>
+ <span class="identifier">y</span> <span class="special">);</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_equal_optional_none"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">==</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">==</span> <span class="special">(</span>
+ <span class="identifier">none_t</span><span class="special">,</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">!</span><span class="identifier">x</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ need not meet requirements of <a href="http://www.sgi.com/tech/stl/EqualityComparable.html" target="_top"><code class="computeroutput"><span class="identifier">EqualityComparable</span></code></a>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_operator_compare_not_equal_optional_none"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">!=</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="special">)</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="keyword">operator</span>
+ <span class="special">!=</span> <span class="special">(</span>
+ <span class="identifier">none_t</span><span class="special">,</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns: </strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">x</span><span class="special">);</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_free_get_pointer"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">auto</span> <span class="identifier">get_pointer</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">o</span>
+ <span class="special">)</span> <span class="special">-></span>
+ <span class="keyword">typename</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">pointer_type</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">auto</span> <span class="identifier">get_pointer</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">o</span> <span class="special">)</span> <span class="special">-></span> <span class="keyword">typename</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">pointer_const_type</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="identifier">o</span><span class="special">.</span><span class="identifier">get_ptr</span><span class="special">()</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_free_get_value_or"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">auto</span> <span class="identifier">get_optional_value_or</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">o</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reference_type</span> <span class="identifier">def</span>
+ <span class="special">)</span> <span class="special">-></span>
+ <span class="keyword">typename</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reference_type</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">auto</span> <span class="identifier">get_optional_value_or</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">o</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reference_const_type</span> <span class="identifier">def</span>
+ <span class="special">)</span> <span class="special">-></span>
+ <span class="keyword">typename</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reference_const_type</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="identifier">o</span><span class="special">.</span><span class="identifier">get_value_or</span><span class="special">(</span><span class="identifier">def</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> This function is deprecated.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_swap_optional_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">swap</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">y</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> Lvalues of type <code class="computeroutput"><span class="identifier">T</span></code> shall be swappable and <code class="computeroutput"><span class="identifier">T</span></code> shall be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>.
+ </li>
+<li class="listitem">
+<p class="simpara">
+ <span class="bold"><strong>Effects:</strong></span>
+ </p>
+<div class="informaltable"><table class="table">
+<colgroup>
+<col>
+<col>
+<col>
+</colgroup>
+<thead><tr></tr></thead>
+<tbody>
+<tr>
+<td>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ calls <code class="computeroutput"><span class="identifier">swap</span><span class="special">(*(*</span><span class="keyword">this</span><span class="special">),</span> <span class="special">*</span><span class="identifier">rhs</span><span class="special">)</span></code>
+ </p>
+ </td>
+<td>
+ <p>
+ initializes the contained value of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> as if direct-initializing
+ an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+ with the expression <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code>, followed by <code class="computeroutput"><span class="identifier">rhs</span><span class="special">.</span><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>,
+ <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ contains a value and <code class="computeroutput"><span class="identifier">rhs</span></code>
+ does not contain a value
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ does not contain a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ initializes the contained value of <code class="computeroutput"><span class="identifier">rhs</span></code>
+ as if direct-initializing an object of type <code class="computeroutput"><span class="identifier">T</span></code> with the expression
+ <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*(*</span><span class="keyword">this</span><span class="special">))</span></code>,
+ followed by <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value
+ and <code class="computeroutput"><span class="identifier">rhs</span></code> contains
+ a value
+ </p>
+ </td>
+<td>
+ <p>
+ no effect
+ </p>
+ </td>
+</tr>
+</tbody>
+</table></div>
+</li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> The states of <code class="computeroutput"><span class="identifier">x</span></code> and <code class="computeroutput"><span class="identifier">y</span></code>
+ interchanged.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> If both are initialized, whatever
+ <code class="computeroutput"><span class="identifier">swap</span><span class="special">(</span><span class="identifier">T</span><span class="special">&,</span><span class="identifier">T</span><span class="special">&)</span></code>
+ throws. If only one is initialized, whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code>
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">(</span><span class="number">12</span><span class="special">);</span>
+<span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">21</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def0</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def1</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">optX</span><span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">optY</span><span class="special">(</span><span class="identifier">y</span><span class="special">);</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">def1</span><span class="special">);</span> <span class="comment">// no-op</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">optX</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def0</span> <span class="special">==</span> <span class="identifier">x</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">optX</span> <span class="special">);</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">def0</span><span class="special">,</span><span class="identifier">optX</span><span class="special">);</span> <span class="comment">// Get back to original values</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">optX</span><span class="special">,</span><span class="identifier">optY</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">optX</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">optY</span> <span class="special">==</span> <span class="identifier">x</span> <span class="special">);</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_swap_optional_reference"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">swap</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>&</span> <span class="identifier">y</span>
+ <span class="special">)</span> <span class="keyword">noexcept</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="identifier">x</span></code>
+ refers to what <code class="computeroutput"><span class="identifier">y</span></code> refererred
+ to before the swap (if anything). <code class="computeroutput"><span class="identifier">y</span></code>
+ refers to whatever <code class="computeroutput"><span class="identifier">x</span></code>
+ referred to before the swap.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">(</span><span class="number">12</span><span class="special">);</span>
+<span class="identifier">T</span> <span class="identifier">y</span><span class="special">(</span><span class="number">21</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">opt0</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">optX</span> <span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">optY</span> <span class="special">(</span><span class="identifier">y</span><span class="special">);</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">optX</span><span class="special">,</span> <span class="identifier">optY</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">optX</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">y</span><span class="special">));</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">optY</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">x</span><span class="special">));</span>
+
+<span class="identifier">boost</span><span class="special">::</span><span class="identifier">swap</span><span class="special">(</span><span class="identifier">opt0</span><span class="special">,</span> <span class="identifier">optX</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt0</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">optX</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">addressof</span><span class="special">(*</span><span class="identifier">opt0</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">y</span><span class="special">));</span>
+</pre>
+ </li>
+</ul></div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2018 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="detailed_semantics___optional_references.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../header__boost_optional_hpp_.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>
diff --git a/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___optional_references.html b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___optional_references.html
new file mode 100644
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--- /dev/null
+++ b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___optional_references.html
@@ -0,0 +1,557 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Detailed Semantics - Optional References</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header <boost/optional/optional.hpp>">
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+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
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+<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="detailed_semantics___optional_values.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="detailed_semantics___free_functions.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics___optional_references"></a><a class="link" href="detailed_semantics___optional_references.html" title="Detailed Semantics - Optional References">Detailed
+ Semantics - Optional References</a>
+</h4></div></div></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_default_ctor"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">()</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span><span class="identifier">none_t</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">false</span></code>; <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> refers to nothing.
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_value_ctor"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">></span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span><span class="identifier">R</span><span class="special">&&</span> <span class="identifier">r</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">true</span></code>; <code class="computeroutput"><span class="identifier">addressof</span><span class="special">(**</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">r</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> Unless <code class="computeroutput"><span class="identifier">R</span></code>
+ is an lvalue reference, the program is ill-formed. This constructor
+ does not participate in overload resolution if <code class="computeroutput"><span class="identifier">decay</span><span class="special"><</span><span class="identifier">R</span><span class="special">></span></code> is an instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> This constructor is declared
+ <code class="computeroutput"><span class="keyword">explicit</span></code> on compilers
+ that do not correctly suport binding to const lvalues of integral types.
+ For more details <a class="link" href="../../dependencies_and_portability/optional_reference_binding.html#optional_reference_binding">see here</a>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">T</span><span class="special">&</span> <span class="identifier">vref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">vref</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="special">++</span> <span class="identifier">v</span> <span class="special">;</span> <span class="comment">// mutate referee</span>
+<span class="identifier">assert</span> <span class="special">(*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span><span class="special">);</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_cond_value_ctor"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">></span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span><span class="special">(</span><span class="keyword">bool</span> <span class="identifier">cond</span><span class="special">,</span> <span class="identifier">R</span><span class="special">&&</span>
+ <span class="identifier">r</span><span class="special">)</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects: </strong></span> Initializes <code class="computeroutput"><span class="identifier">ref</span></code> with expression <code class="computeroutput"><span class="identifier">cond</span> <span class="special">?</span>
+ <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">r</span><span class="special">)</span> <span class="special">:</span> <span class="keyword">nullptr</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">cond</span></code>; If <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>, <code class="computeroutput"><span class="identifier">addressof</span><span class="special">(**</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">addressof</span><span class="special">(</span><span class="identifier">r</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> Unless <code class="computeroutput"><span class="identifier">R</span></code>
+ is an lvalue reference, the program is ill-formed. This constructor
+ does not participate in overload resolution if <code class="computeroutput"><span class="identifier">decay</span><span class="special"><</span><span class="identifier">R</span><span class="special">></span></code> is an instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span></code>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_copy_ctor"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span> <span class="special">(</span>
+ <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="keyword">noexcept</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects: </strong></span> Initializes <code class="computeroutput"><span class="identifier">ref</span></code> with expression <code class="computeroutput"><span class="identifier">rhs</span><span class="special">.</span><span class="identifier">ref</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">uninit</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">uninit</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span>
+
+<span class="identifier">T</span> <span class="identifier">v</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">ref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init</span><span class="special">(</span><span class="identifier">ref</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">v</span> <span class="special">=</span> <span class="number">3</span> <span class="special">;</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init2</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_ctor_from_opt_U"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">optional</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">&></span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">rhs</span> <span class="special">)</span>
+ <span class="keyword">noexcept</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_convertible</span><span class="special"><</span><span class="identifier">U</span><span class="special">&,</span> <span class="identifier">T</span><span class="special">&>::</span><span class="identifier">value</span></code>
+ is <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effects: </strong></span> Initializes <code class="computeroutput"><span class="identifier">ref</span></code> with expression <code class="computeroutput"><span class="identifier">rhs</span><span class="special">.</span><span class="identifier">ref</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span></code>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_assign_none_t"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">none_t</span>
+ <span class="special">)</span> <span class="keyword">noexcept</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects: </strong></span> Assigns <code class="computeroutput"><span class="identifier">ref</span></code>
+ with expression <code class="computeroutput"><span class="keyword">nullptr</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">false</span></code>.
+ </li>
+</ul></div>
+<a name="reference_optional_ref_copy_assign"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">rhs</span> <span class="special">)</span>
+ <span class="keyword">noexcept</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects: </strong></span> Assigns <code class="computeroutput"><span class="identifier">ref</span></code>
+ with expression <code class="computeroutput"><span class="identifier">rhs</span><span class="special">.</span><span class="identifier">ref</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> This behaviour is called <span class="emphasis"><em>rebinding
+ semantics</em></span>. See <a class="link" href="../../tutorial/optional_references/rebinding_semantics_for_assignment_of_optional_references.html" title="Rebinding semantics for assignment of optional references">here</a>
+ for details.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
+<span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">ora</span><span class="special">(</span><span class="identifier">ra</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">orb</span><span class="special">(</span><span class="identifier">rb</span><span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">orb</span> <span class="special">;</span> <span class="comment">// binds 'def' to 'b' through 'rb' wrapped within 'orb'</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">b</span> <span class="special">)</span> <span class="special">;</span>
+<span class="special">*</span><span class="identifier">def</span> <span class="special">=</span> <span class="identifier">ora</span> <span class="special">;</span> <span class="comment">// changes the value of 'b' to a copy of the value of 'a'</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">b</span> <span class="special">==</span> <span class="identifier">a</span> <span class="special">)</span> <span class="special">;</span>
+<span class="keyword">int</span> <span class="identifier">c</span> <span class="special">=</span> <span class="number">3</span><span class="special">;</span>
+<span class="keyword">int</span><span class="special">&</span> <span class="identifier">rc</span> <span class="special">=</span> <span class="identifier">c</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">orc</span><span class="special">(</span><span class="identifier">rc</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">ora</span> <span class="special">=</span> <span class="identifier">orc</span> <span class="special">;</span> <span class="comment">// REBINDS ora to 'c' through 'rc'</span>
+<span class="identifier">c</span> <span class="special">=</span> <span class="number">4</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">ora</span> <span class="special">==</span> <span class="number">4</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<a name="reference_optional_ref_assign_optional_U"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">&></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="keyword">noexcept</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_convertible</span><span class="special"><</span><span class="identifier">U</span><span class="special">&,</span> <span class="identifier">T</span><span class="special">&>::</span><span class="identifier">value</span></code>
+ is <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effects: </strong></span> Assigns <code class="computeroutput"><span class="identifier">ref</span></code>
+ with expression <code class="computeroutput"><span class="identifier">rhs</span><span class="special">.</span><span class="identifier">ref</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span></code>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_assign_R"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">R</span><span class="special">&&</span> <span class="identifier">r</span>
+ <span class="special">)</span> <span class="keyword">noexcept</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects: </strong></span> Assigns <code class="computeroutput"><span class="identifier">ref</span></code>
+ with expression <code class="computeroutput"><span class="identifier">r</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> Unless <code class="computeroutput"><span class="identifier">R</span></code>
+ is an lvalue reference, the program is ill-formed. This function does
+ not participate in overload resolution if <code class="computeroutput"><span class="identifier">decay</span><span class="special"><</span><span class="identifier">R</span><span class="special">></span></code> is an instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">a</span> <span class="special">=</span> <span class="number">1</span> <span class="special">;</span>
+<span class="keyword">int</span> <span class="identifier">b</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&</span> <span class="identifier">ra</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&</span> <span class="identifier">rb</span> <span class="special">=</span> <span class="identifier">b</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">&></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">ra</span><span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">rb</span> <span class="special">;</span> <span class="comment">// binds 'def' to 'b' through 'rb'</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">b</span> <span class="special">)</span> <span class="special">;</span>
+<span class="special">*</span><span class="identifier">def</span> <span class="special">=</span> <span class="identifier">a</span> <span class="special">;</span> <span class="comment">// changes the value of 'b' to a copy of the value of 'a'</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">b</span> <span class="special">==</span> <span class="identifier">a</span> <span class="special">)</span> <span class="special">;</span>
+<span class="keyword">int</span> <span class="identifier">c</span> <span class="special">=</span> <span class="number">3</span><span class="special">;</span>
+<span class="keyword">int</span><span class="special">&</span> <span class="identifier">rc</span> <span class="special">=</span> <span class="identifier">c</span> <span class="special">;</span>
+<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">rc</span> <span class="special">;</span> <span class="comment">// REBINDS to 'c' through 'rc'</span>
+<span class="identifier">c</span> <span class="special">=</span> <span class="number">4</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="number">4</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_emplace_R"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">emplace</span><span class="special">(</span> <span class="identifier">R</span><span class="special">&&</span> <span class="identifier">r</span>
+ <span class="special">)</span> <span class="keyword">noexcept</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects: </strong></span> Assigns <code class="computeroutput"><span class="identifier">ref</span></code>
+ with expression <code class="computeroutput"><span class="identifier">r</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> Unless <code class="computeroutput"><span class="identifier">R</span></code>
+ is an lvalue reference, the program is ill-formed. This function does
+ not participate in overload resolution if <code class="computeroutput"><span class="identifier">decay</span><span class="special"><</span><span class="identifier">R</span><span class="special">></span></code> is an instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span></code>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_get"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span> <span class="special">*()</span>
+ <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effects: </strong></span> Returns <code class="computeroutput"><span class="special">*</span><span class="identifier">ref</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws: </strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">T</span><span class="special">&</span> <span class="identifier">vref</span> <span class="special">=</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">vref</span> <span class="special">);</span>
+<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">vref2</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">opt</span><span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">vref2</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="special">++</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_arrow"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">*</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span> <span class="special">-></span>
+ <span class="special">()</span> <span class="keyword">const</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effects: </strong></span> Returns <code class="computeroutput"><span class="identifier">ref</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws: </strong></span> Nothing.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">value</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">?</span> <span class="special">*</span><span class="identifier">val</span> <span class="special">:</span> <span class="keyword">throw</span> <span class="identifier">bad_optional_access</span><span class="special">();</span></code>.
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_value_or"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">></span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">value_or</span><span class="special">(</span> <span class="identifier">R</span><span class="special">&&</span> <span class="identifier">r</span>
+ <span class="special">)</span> <span class="keyword">const</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">if</span> <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="special">**</span><span class="keyword">this</span><span class="special">;</span> <span class="keyword">else</span> <span class="keyword">return</span>
+ <span class="identifier">r</span><span class="special">;</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> Unless <code class="computeroutput"><span class="identifier">R</span></code>
+ is an lvalue reference, the program is ill-formed.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_value_or_eval"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">value_or</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">if</span> <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="special">**</span><span class="keyword">this</span><span class="special">;</span> <span class="keyword">else</span> <span class="keyword">return</span>
+ <span class="identifier">f</span><span class="special">();</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> Unless <code class="computeroutput"><span class="keyword">decltype</span><span class="special">(</span><span class="identifier">f</span><span class="special">())</span></code> is an lvalue reference, the program
+ is ill-formed.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_map"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="keyword">auto</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">map</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="keyword">const</span> <span class="special">-></span> </code><span class="emphasis"><em>see below</em></span><code class="computeroutput"><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">if</span> <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="identifier">f</span><span class="special">(**</span><span class="keyword">this</span><span class="special">);</span> <span class="keyword">else</span> <span class="keyword">return</span> <span class="identifier">none</span><span class="special">;</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> The return type of this function
+ is <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">decltype</span><span class="special">(</span><span class="identifier">f</span><span class="special">(**</span><span class="keyword">this</span><span class="special">))></span></code>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_flat_map"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="keyword">auto</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">flat_map</span><span class="special">(</span>
+ <span class="identifier">F</span> <span class="identifier">f</span>
+ <span class="special">)</span> <span class="keyword">const</span>
+ <span class="special">-></span> </code><span class="emphasis"><em>see below</em></span><code class="computeroutput"><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> The return type of expression
+ <code class="computeroutput"><span class="identifier">f</span><span class="special">(**</span><span class="keyword">this</span><span class="special">)</span></code>
+ is <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span></code>
+ for some object or reference type <code class="computeroutput"><span class="identifier">U</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">if</span> <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="identifier">f</span><span class="special">(**</span><span class="keyword">this</span><span class="special">);</span> <span class="keyword">else</span> <span class="keyword">return</span> <span class="identifier">none</span><span class="special">;</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> The return type of this function
+ is <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span></code>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_get_ptr"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">*</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">get_ptr</span> <span class="special">()</span>
+ <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="identifier">ref</span></code>.
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_operator_bool"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="identifier">has_value</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span> <span class="keyword">bool</span>
+ <span class="special">()</span> <span class="keyword">const</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">ref</span><span class="special">)</span></code>.
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_operator_not"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="keyword">operator</span> <span class="special">!</span> <span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">!</span><span class="keyword">bool</span><span class="special">(</span><span class="identifier">ref</span><span class="special">)</span></code>.
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_reset"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">reset</span><span class="special">()</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Use <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span> <span class="special">=</span> <span class="identifier">none</span></code> instead.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> This function is depprecated.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_reset_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">></span> <span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">reset</span> <span class="special">(</span> <span class="identifier">R</span><span class="special">&&</span>
+ <span class="identifier">r</span><span class="special">)</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">R</span><span class="special">>(</span><span class="identifier">r</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> This function is depprecated.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_is_initialized"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">is_initialized</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> This function is depprecated.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_ref_get_value_or_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">></span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&>::</span><span class="identifier">get_value_or</span><span class="special">(</span> <span class="identifier">R</span><span class="special">&&</span> <span class="identifier">r</span>
+ <span class="special">)</span> <span class="keyword">const</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="identifier">value_or</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">R</span><span class="special">>(</span><span class="identifier">r</span><span class="special">);</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> This function is depprecated.
+ </li>
+</ul></div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2018 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="detailed_semantics___optional_values.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="detailed_semantics___free_functions.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>
diff --git a/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___optional_values.html b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/detailed_semantics___optional_values.html
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@@ -0,0 +1,1788 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Detailed Semantics - Optional Values</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header <boost/optional/optional.hpp>">
+<link rel="prev" href="header_optional_optional_refs.html" title="Optional References">
+<link rel="next" href="detailed_semantics___optional_references.html" title="Detailed Semantics - Optional References">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
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+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="header_optional_optional_refs.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="detailed_semantics___optional_references.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.detailed_semantics___optional_values"></a><a class="link" href="detailed_semantics___optional_values.html" title="Detailed Semantics - Optional Values">Detailed
+ Semantics - Optional Values</a>
+</h4></div></div></div>
+<div class="note"><table border="0" summary="Note">
+<tr>
+<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../../doc/src/images/note.png"></td>
+<th align="left">Note</th>
+</tr>
+<tr><td align="left" valign="top"><p>
+ The following section contains various <code class="computeroutput"><span class="identifier">assert</span><span class="special">()</span></code> which are used only to show the postconditions
+ as sample code. It is not implied that the type <code class="computeroutput"><span class="identifier">T</span></code>
+ must support each particular expression but that if the expression is
+ supported, the implied condition holds.
+ </p></td></tr>
+</table></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">()</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Default-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">uninitialized</span>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> T's default constructor <span class="underline">is not</span> called.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_none_t"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">none_t</span> <span class="special">)</span>
+ <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Constructs an <code class="computeroutput"><span class="identifier">optional</span></code> uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">uninitialized</span>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>'s
+ default constructor <span class="underline">is not</span> called.
+ The expression <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none</span></code>
+ denotes an instance of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none_t</span></code>
+ that can be used as the parameter.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">none</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">n</span><span class="special">(</span><span class="identifier">none</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">n</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_copy_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
+ is <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Directly-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
+ and its value is a <span class="emphasis"><em>copy</em></span> of <code class="computeroutput"><span class="identifier">v</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span></code> throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span></code> is called.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">);</span></code> in that case, this constructor
+ has no effect.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_move_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">T</span><span class="special">&&</span>
+ <span class="identifier">v</span> <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
+ is <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Directly-Move-Constructs an
+ <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
+ and its value is move-constructed from <code class="computeroutput"><span class="identifier">v</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code>
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code>
+ is called.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">);</span></code>
+ in that case, the state of <code class="computeroutput"><span class="identifier">v</span></code>
+ is determined by exception safety guarantees for <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span><span class="special">&&)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v1</span><span class="special">,</span> <span class="identifier">v2</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">v1</span><span class="special">));</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">v2</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_bool_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ If condition is true, same as:
+ </li></ul></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ otherwise, same as:
+ </li></ul></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">()</span></code>
+ </p></blockquote></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span>
+ <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_copy_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
+ is <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Copy-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> If rhs is initialized,
+ <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initialized and its value is a <span class="emphasis"><em>copy</em></span> of the
+ value of <code class="computeroutput"><span class="identifier">rhs</span></code>; else
+ <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span></code> throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If rhs is initialized, <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span></code>
+ is called.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">);</span></code> in that case, this constructor
+ has no effect.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">uninit</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">uninit</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init</span><span class="special">(</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">init</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_move_constructor_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span>
+ <span class="identifier">optional</span><span class="special">&&</span>
+ <span class="identifier">rhs</span> <span class="special">)</span>
+ <span class="keyword">noexcept</span><span class="special">(</span></code><span class="emphasis"><em>see
+ below</em></span><code class="computeroutput"><span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>
+ is <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Move-constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initialized and its value is move constructed from <code class="computeroutput"><span class="identifier">rhs</span></code>; else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code>
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> The expression inside <code class="computeroutput"><span class="keyword">noexcept</span></code> is equivalent to <code class="computeroutput"><span class="identifier">is_nothrow_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span> <span class="special">&&</span>
+ <span class="special">)</span></code> is called.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">);</span></code>
+ in that case, <code class="computeroutput"><span class="identifier">rhs</span></code> remains
+ initialized and the value of <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by exception safety
+ of <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span><span class="special">&&)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">uninit</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">uninit</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">uinit2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">uninit</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">uninit2</span> <span class="special">==</span> <span class="identifier">uninit</span> <span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">init</span><span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">uniqye_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>(</span><span class="keyword">new</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_ptr</span><span class="special"><</span><span class="identifier">T</span><span class="special">>></span> <span class="identifier">init2</span> <span class="special">(</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">init</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">init</span> <span class="special">==</span> <span class="keyword">nullptr</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">init2</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">**</span><span class="identifier">init2</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span>
+ <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Copy-Constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initialized and its value is a <span class="emphasis"><em>copy</em></span> of the
+ value of rhs converted to type <code class="computeroutput"><span class="identifier">T</span></code>;
+ else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span></code> throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span></code> is called if <code class="computeroutput"><span class="identifier">rhs</span></code> is initialized, which requires
+ a valid conversion from <code class="computeroutput"><span class="identifier">U</span></code>
+ to <code class="computeroutput"><span class="identifier">T</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">);</span></code> in that case, this constructor
+ has no effect.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span><span class="number">123.4</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="number">123.4</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span><span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="number">123</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_move_constructor_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">>&&</span> <span class="identifier">rhs</span>
+ <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Move-constructs an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> If <code class="computeroutput"><span class="identifier">rhs</span></code>
+ is initialized, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initialized and its value is move-constructed from <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>;
+ else <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">)</span></code>
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">)</span></code>
+ is called if <code class="computeroutput"><span class="identifier">rhs</span></code> is
+ initialized, which requires a valid conversion from <code class="computeroutput"><span class="identifier">U</span></code>
+ to <code class="computeroutput"><span class="identifier">T</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span> <span class="special">);</span></code>
+ in that case, <code class="computeroutput"><span class="identifier">rhs</span></code> remains
+ initialized and the value of <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by exception safety
+ guarantee of <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span> <span class="identifier">U</span><span class="special">&&</span>
+ <span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span><span class="number">123.4</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="number">123.4</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">x</span><span class="special">))</span> <span class="special">;</span>
+<span class="identifier">assert</span><span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="number">123</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_in_place_init"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">></span>
+ <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">in_place_init_t</span><span class="special">,</span> <span class="identifier">Args</span><span class="special">&&...</span> <span class="identifier">ars</span>
+ <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_constructible_v</span><span class="special"><</span><span class="identifier">T</span><span class="special">,</span> <span class="identifier">Args</span><span class="special">&&...></span></code> is <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Initializes the contained
+ value as if direct-non-list-initializing an object of type <code class="computeroutput"><span class="identifier">T</span></code> with the arguments <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">Args</span><span class="special">>(</span><span class="identifier">args</span><span class="special">)...</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Any exception thrown by the
+ selected constructor of <code class="computeroutput"><span class="identifier">T</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ need not be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>.
+ On compilers that do not suppor variadic templates or rvalue references,
+ this constuctor is available in limited functionality. For details
+ <a class="link" href="../../dependencies_and_portability/emplace_operations_in_older_compilers.html#optional_emplace_workaround">see here</a>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="comment">// creates an std::mutex using its default constructor</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">mutex</span><span class="special">></span> <span class="identifier">om</span> <span class="special">{</span><span class="identifier">in_place_init</span><span class="special">};</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">om</span><span class="special">);</span>
+
+<span class="comment">// creates a unique_lock by calling unique_lock(*om, std::defer_lock)</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">unique_lock</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">mutex</span><span class="special">>></span> <span class="identifier">ol</span> <span class="special">{</span><span class="identifier">in_place_init</span><span class="special">,</span> <span class="special">*</span><span class="identifier">om</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">defer_lock</span><span class="special">};</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">ol</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">ol</span><span class="special">-></span><span class="identifier">owns_lock</span><span class="special">());</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_in_place_init_if"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">></span>
+ <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">in_place_init_if_t</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span>
+ <span class="identifier">Args</span><span class="special">&&...</span>
+ <span class="identifier">ars</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">is_constructible_v</span><span class="special"><</span><span class="identifier">T</span><span class="special">,</span> <span class="identifier">Args</span><span class="special">&&...></span></code> is <code class="computeroutput"><span class="keyword">true</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> If <code class="computeroutput"><span class="identifier">condition</span></code>
+ is <code class="computeroutput"><span class="keyword">true</span></code>, initializes the
+ contained value as if direct-non-list-initializing an object of type
+ <code class="computeroutput"><span class="identifier">T</span></code> with the arguments
+ <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">Args</span><span class="special">>(</span><span class="identifier">args</span><span class="special">)...</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">==</span> <span class="identifier">condition</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Any exception thrown by the
+ selected constructor of <code class="computeroutput"><span class="identifier">T</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes: </strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ need not be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>.
+ On compilers that do not suppor variadic templates or rvalue references,
+ this constuctor is available in limited functionality. For details
+ <a class="link" href="../../dependencies_and_portability/emplace_operations_in_older_compilers.html#optional_emplace_workaround">see here</a>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">>></span> <span class="identifier">ov1</span> <span class="special">{</span><span class="identifier">in_place_init_if</span><span class="special">,</span> <span class="keyword">false</span><span class="special">,</span> <span class="number">3</span><span class="special">,</span> <span class="string">"A"</span><span class="special">};</span>
+<span class="identifier">assert</span> <span class="special">(!</span><span class="identifier">ov1</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">>></span> <span class="identifier">ov2</span> <span class="special">{</span><span class="identifier">in_place_init_if</span><span class="special">,</span> <span class="keyword">true</span><span class="special">,</span> <span class="number">3</span><span class="special">,</span> <span class="string">"A"</span><span class="special">};</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">ov2</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">ov2</span><span class="special">-></span><span class="identifier">size</span><span class="special">()</span> <span class="special">==</span> <span class="number">3</span><span class="special">);</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_constructor_factory"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">InPlaceFactory</span><span class="special">></span>
+ <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">InPlaceFactory</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">f</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">TypedInPlaceFactory</span><span class="special">></span>
+ <span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">optional</span><span class="special">(</span> <span class="identifier">TypedInPlaceFactory</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">f</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Constructs an <code class="computeroutput"><span class="identifier">optional</span></code> with a value of <code class="computeroutput"><span class="identifier">T</span></code> obtained from the factory.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
+ and its value is <span class="emphasis"><em>directly given</em></span> from the factory
+ <code class="computeroutput"><span class="identifier">f</span></code> (i.e., the value
+ <span class="underline">is not copied</span>).
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever the <code class="computeroutput"><span class="identifier">T</span></code> constructor called by the factory
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> See <a class="link" href="../../tutorial/in_place_factories.html" title="In-Place Factories">In-Place
+ Factories</a>
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during the call to the <code class="computeroutput"><span class="identifier">T</span></code>
+ constructor used by the factory; in that case, this constructor has
+ no effect.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">C</span> <span class="special">{</span> <span class="identifier">C</span> <span class="special">(</span> <span class="keyword">char</span><span class="special">,</span> <span class="keyword">double</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="special">)</span> <span class="special">;</span> <span class="special">}</span> <span class="special">;</span>
+
+<span class="identifier">C</span> <span class="identifier">v</span><span class="special">(</span><span class="char">'A'</span><span class="special">,</span><span class="number">123.4</span><span class="special">,</span><span class="string">"hello"</span><span class="special">);</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">C</span><span class="special">></span> <span class="identifier">x</span><span class="special">(</span> <span class="identifier">in_place</span> <span class="special">(</span><span class="char">'A'</span><span class="special">,</span> <span class="number">123.4</span><span class="special">,</span> <span class="string">"hello"</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// InPlaceFactory used</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">C</span><span class="special">></span> <span class="identifier">y</span><span class="special">(</span> <span class="identifier">in_place</span><span class="special"><</span><span class="identifier">C</span><span class="special">>(</span><span class="char">'A'</span><span class="special">,</span> <span class="number">123.4</span><span class="special">,</span> <span class="string">"hello"</span><span class="special">)</span> <span class="special">);</span> <span class="comment">// TypedInPlaceFactory used</span>
+
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">x</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">y</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_equal_none_t"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">none_t</span>
+ <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized destroys its contained
+ value.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_equal_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Assigns the value <code class="computeroutput"><span class="identifier">rhs</span></code> to an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and its value is
+ a <span class="emphasis"><em>copy</em></span> of <code class="computeroutput"><span class="identifier">rhs</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">)</span></code> or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&)</span></code>
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s assignment operator is used,
+ otherwise, its copy-constructor is used.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> In the event of
+ an exception, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified
+ as far as <code class="computeroutput"><span class="identifier">optional</span></code>
+ is concerned (it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s
+ <code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>).
+ If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s
+ <span class="emphasis"><em>copy constructor</em></span> fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">T</span> <span class="identifier">y</span><span class="special">;</span>
+<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">y</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">y</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">y</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_move_equal_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Moves the value <code class="computeroutput"><span class="identifier">rhs</span></code> to an <code class="computeroutput"><span class="identifier">optional</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized and its value is
+ moved from <code class="computeroutput"><span class="identifier">rhs</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="special">)</span></code>
+ or <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">T</span><span class="special">(</span><span class="identifier">T</span> <span class="special">&&)</span></code>
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> was initialized, <code class="computeroutput"><span class="identifier">T</span></code>'s move-assignment operator is used,
+ otherwise, its move-constructor is used.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> In the event of
+ an exception, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is unchanged and its value unspecified
+ as far as <code class="computeroutput"><span class="identifier">optional</span></code>
+ is concerned (it is up to <code class="computeroutput"><span class="identifier">T</span></code>'s
+ <code class="computeroutput"><span class="keyword">operator</span><span class="special">=()</span></code>).
+ If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is initially uninitialized and <code class="computeroutput"><span class="identifier">T</span></code>'s
+ <span class="emphasis"><em>move constructor</em></span> fails, <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is left properly uninitialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">x</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">T</span> <span class="identifier">y1</span><span class="special">,</span> <span class="identifier">y2</span><span class="special">,</span> <span class="identifier">yR</span><span class="special">;</span>
+<span class="identifier">def</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">y1</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">def</span> <span class="special">==</span> <span class="identifier">yR</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">y2</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">yR</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_equal_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">rhs</span> <span class="special">)</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ is <a href="../../../../../../utility/CopyConstructible.html" target="_top"><code class="computeroutput"><span class="identifier">CopyConstructible</span></code></a> and <code class="computeroutput"><span class="identifier">CopyAssignable</span></code>.
+ </li>
+<li class="listitem">
+<p class="simpara">
+ <span class="bold"><strong>Effects:</strong></span>
+ </p>
+<div class="informaltable"><table class="table">
+<colgroup>
+<col>
+<col>
+<col>
+</colgroup>
+<thead><tr></tr></thead>
+<tbody>
+<tr>
+<td>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ assigns <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
+ to the contained value
+ </p>
+ </td>
+<td>
+ <p>
+ initializes the contained value as if direct-initializing
+ an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+ with <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ does not contain a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>
+ </p>
+ </td>
+<td>
+ <p>
+ no effect
+ </p>
+ </td>
+</tr>
+</tbody>
+</table></div>
+</li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>;
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> If any exception
+ is thrown, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">rhs</span></code>
+ remains unchanged. If an exception is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s copy constructor, no effect.
+ If an exception is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s
+ copy assignment, the state of its contained value is as defined by
+ the exception safety guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s
+ copy assignment.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
+
+<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span>
+<span class="comment">// previous value (copy of 'v') destroyed from within 'opt'.</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_move_equal_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span></code><span class="emphasis"><em>see below</em></span><code class="computeroutput"><span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ is <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>
+ and <code class="computeroutput"><span class="identifier">MoveAssignable</span></code>.
+ </li>
+<li class="listitem">
+<p class="simpara">
+ <span class="bold"><strong>Effects:</strong></span>
+ </p>
+<div class="informaltable"><table class="table">
+<colgroup>
+<col>
+<col>
+<col>
+</colgroup>
+<thead><tr></tr></thead>
+<tbody>
+<tr>
+<td>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ assigns <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code> to the contained value
+ </p>
+ </td>
+<td>
+ <p>
+ initializes the contained value as if direct-initializing
+ an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+ with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ does not contain a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>
+ </p>
+ </td>
+<td>
+ <p>
+ no effect
+ </p>
+ </td>
+</tr>
+</tbody>
+</table></div>
+</li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>;
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> The expression inside <code class="computeroutput"><span class="keyword">noexcept</span></code> is equivalent to <code class="computeroutput"><span class="identifier">is_nothrow_move_constructible</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span> <span class="special">&&</span>
+ <span class="identifier">is_nothrow_move_assignable</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> If any exception
+ is thrown, the initialization state of <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="identifier">rhs</span></code>
+ remains unchanged. If an exception is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s move constructor, the state of
+ <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
+ is determined by the exception safety guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s
+ move constructor. If an exception is thrown during the call to T's
+ move-assignment, the state of <code class="computeroutput"><span class="special">**</span><span class="keyword">this</span></code> and <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code> is determined by the exception
+ safety guarantee of T's move assignment.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">))</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
+
+<span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">T</span><span class="special">(</span><span class="number">2</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_equal_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+<p class="simpara">
+ <span class="bold"><strong>Effect:</strong></span>
+ </p>
+<div class="informaltable"><table class="table">
+<colgroup>
+<col>
+<col>
+<col>
+</colgroup>
+<thead><tr></tr></thead>
+<tbody>
+<tr>
+<td>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ assigns <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
+ to the contained value
+ </p>
+ </td>
+<td>
+ <p>
+ initializes the contained value as if direct-initializing
+ an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+ with <code class="computeroutput"><span class="special">*</span><span class="identifier">rhs</span></code>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ does not contain a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>
+ </p>
+ </td>
+<td>
+ <p>
+ no effect
+ </p>
+ </td>
+</tr>
+</tbody>
+</table></div>
+</li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> If any exception
+ is thrown, the result of the expression <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code> remains unchanged. If an exception
+ is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s
+ constructor, no effect. If an exception is thrown during the call to
+ <code class="computeroutput"><span class="identifier">T</span></code>'s assignment, the
+ state of its contained value is as defined by the exception safety
+ guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s copy
+ assignment.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt0</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">opt1</span><span class="special">;</span>
+
+<span class="identifier">opt1</span> <span class="special">=</span> <span class="identifier">opt0</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt1</span> <span class="special">==</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_move_equal_other_optional"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">>&&</span> <span class="identifier">rhs</span>
+ <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+<p class="simpara">
+ <span class="bold"><strong>Effect:</strong></span>
+ </p>
+<div class="informaltable"><table class="table">
+<colgroup>
+<col>
+<col>
+<col>
+</colgroup>
+<thead><tr></tr></thead>
+<tbody>
+<tr>
+<td>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> does not contain a value</strong></span>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ contains a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ assigns <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code> to the contained value
+ </p>
+ </td>
+<td>
+ <p>
+ initializes the contained value as if direct-initializing
+ an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+ with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">rhs</span><span class="special">)</span></code>
+ </p>
+ </td>
+</tr>
+<tr>
+<td>
+ <p>
+ <span class="bold"><strong><code class="computeroutput"><span class="identifier">rhs</span></code>
+ does not contain a value</strong></span>
+ </p>
+ </td>
+<td>
+ <p>
+ destroys the contained value by calling <code class="computeroutput"><span class="identifier">val</span><span class="special">-></span><span class="identifier">T</span><span class="special">::~</span><span class="identifier">T</span><span class="special">()</span></code>
+ </p>
+ </td>
+<td>
+ <p>
+ no effect
+ </p>
+ </td>
+</tr>
+</tbody>
+</table></div>
+</li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions:</strong></span> <code class="computeroutput"><span class="keyword">bool</span><span class="special">(</span><span class="identifier">rhs</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> If any exception
+ is thrown, the result of the expression <code class="computeroutput"><span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span></code> remains unchanged. If an exception
+ is thrown during the call to <code class="computeroutput"><span class="identifier">T</span></code>'s
+ constructor, no effect. If an exception is thrown during the call to
+ <code class="computeroutput"><span class="identifier">T</span></code>'s assignment, the
+ state of its contained value is as defined by the exception safety
+ guarantee of <code class="computeroutput"><span class="identifier">T</span></code>'s copy
+ assignment.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt0</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="identifier">opt1</span><span class="special">;</span>
+
+<span class="identifier">opt1</span> <span class="special">=</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(</span><span class="identifier">opt0</span><span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt0</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt1</span> <span class="special">)</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt1</span> <span class="special">==</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_emplace"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">></span>
+ <span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">emplace</span><span class="special">(</span> <span class="identifier">Args</span><span class="special">&&...</span> <span class="identifier">args</span>
+ <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> The compiler supports rvalue
+ references and variadic templates.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized calls <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span> <span class="special">=</span> <span class="identifier">none</span></code>.
+ Then initializes in-place the contained value as if direct-initializing
+ an object of type <code class="computeroutput"><span class="identifier">T</span></code>
+ with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">Args</span><span class="special">>(</span><span class="identifier">args</span><span class="special">)...</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever the selected <code class="computeroutput"><span class="identifier">T</span></code>'s constructor throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> If an exception
+ is thrown during the initialization of <code class="computeroutput"><span class="identifier">T</span></code>,
+ <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>
+ is <span class="emphasis"><em>uninitialized</em></span>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ need not be <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>
+ or <code class="computeroutput"><span class="identifier">MoveAssignable</span></code>.
+ On compilers that do not suppor variadic templates or rvalue references,
+ this function is available in limited functionality. For details <a class="link" href="../../dependencies_and_portability/emplace_operations_in_older_compilers.html#optional_emplace_workaround">see here</a>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">const</span> <span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">;</span>
+<span class="identifier">opt</span><span class="special">.</span><span class="identifier">emplace</span><span class="special">(</span><span class="number">0</span><span class="special">);</span> <span class="comment">// create in-place using ctor T(int)</span>
+<span class="identifier">opt</span><span class="special">.</span><span class="identifier">emplace</span><span class="special">();</span> <span class="comment">// destroy previous and default-construct another T</span>
+<span class="identifier">opt</span><span class="special">.</span><span class="identifier">emplace</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span> <span class="comment">// destroy and copy-construct in-place (no assignment called)</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_equal_factory"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">InPlaceFactory</span><span class="special">></span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">InPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="identifier">TypedInPlaceFactory</span><span class="special">></span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">=(</span> <span class="identifier">TypedInPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">);</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Assigns an <code class="computeroutput"><span class="identifier">optional</span></code>
+ with a value of <code class="computeroutput"><span class="identifier">T</span></code> obtained
+ from the factory.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Postconditions: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is <span class="underline">initialized</span>
+ and its value is <span class="emphasis"><em>directly given</em></span> from the factory
+ <code class="computeroutput"><span class="identifier">f</span></code> (i.e., the value
+ <span class="underline">is not copied</span>).
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Whatever the <code class="computeroutput"><span class="identifier">T</span></code> constructor called by the factory
+ throws.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> See <a class="link" href="../../tutorial/in_place_factories.html" title="In-Place Factories">In-Place
+ Factories</a>
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Exception Safety:</strong></span> Exceptions can only
+ be thrown during the call to the <code class="computeroutput"><span class="identifier">T</span></code>
+ constructor used by the factory; in that case, the <code class="computeroutput"><span class="identifier">optional</span></code>
+ object will be reset to be <span class="emphasis"><em>uninitialized</em></span>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_reset_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reset</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Deprecated:</strong></span> same as <code class="computeroutput"><span class="keyword">operator</span><span class="special">=</span>
+ <span class="special">(</span> <span class="identifier">T</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">v</span><span class="special">)</span>
+ <span class="special">;</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_reset"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">void</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">reset</span><span class="special">()</span> <span class="keyword">noexcept</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Deprecated:</strong></span> Same as <code class="computeroutput"><span class="keyword">operator</span><span class="special">=(</span>
+ <span class="identifier">none_t</span> <span class="special">);</span></code>
+ </li></ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_get"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">get</span><span class="special">()</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="identifier">get</span> <span class="special">(</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">inline</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get</span>
+ <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="special">&)</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> A reference to the contained
+ value
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The requirement is asserted
+ via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_asterisk"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">*()</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">*()</span>
+ <span class="special">&;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> A reference to the contained
+ value
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The requirement is asserted
+ via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
+ On compilers that do not support ref-qualifiers on member functions
+ these two overloads are replaced with the classical two: a <code class="computeroutput"><span class="keyword">const</span></code> and non-<code class="computeroutput"><span class="keyword">const</span></code>
+ member functions.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span>
+<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">u</span> <span class="special">=</span> <span class="special">*</span><span class="identifier">opt</span><span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">u</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">T</span> <span class="identifier">w</span> <span class="special">;</span>
+<span class="special">*</span><span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">w</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">opt</span> <span class="special">==</span> <span class="identifier">w</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_asterisk_move"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">*()</span>
+ <span class="special">&&;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> contains a value.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">val</span><span class="special">);</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The requirement is asserted
+ via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
+ On compilers that do not support ref-qualifiers on member functions
+ this overload is not present.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span><span class="special">()</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span><span class="special">()</span> <span class="special">&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">?</span> <span class="special">*</span><span class="identifier">val</span> <span class="special">:</span> <span class="keyword">throw</span> <span class="identifier">bad_optional_access</span><span class="special">();</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ ref-qualifiers on member functions these two overloads are replaced
+ with the classical two: a <code class="computeroutput"><span class="keyword">const</span></code>
+ and non-<code class="computeroutput"><span class="keyword">const</span></code> member functions.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">o0</span><span class="special">,</span> <span class="identifier">o1</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">o1</span><span class="special">.</span><span class="identifier">value</span><span class="special">()</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">);</span>
+
+<span class="keyword">try</span> <span class="special">{</span>
+ <span class="identifier">o0</span><span class="special">.</span><span class="identifier">value</span><span class="special">();</span> <span class="comment">// throws</span>
+ <span class="identifier">assert</span> <span class="special">(</span> <span class="keyword">false</span> <span class="special">);</span>
+<span class="special">}</span>
+<span class="keyword">catch</span><span class="special">(</span><span class="identifier">bad_optional_access</span><span class="special">&)</span> <span class="special">{</span>
+ <span class="identifier">assert</span> <span class="special">(</span> <span class="keyword">true</span> <span class="special">);</span>
+<span class="special">}</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_value_move"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span><span class="special">()</span> <span class="special">&&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">return</span> <span class="keyword">bool</span><span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="special">?</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(*</span><span class="identifier">val</span><span class="special">)</span> <span class="special">:</span> <span class="keyword">throw</span> <span class="identifier">bad_optional_access</span><span class="special">();</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ ref-qualifiers on member functions this overload is not present.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_value_or"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or</span><span class="special">(</span><span class="identifier">U</span> <span class="special">&&</span>
+ <span class="identifier">v</span><span class="special">)</span>
+ <span class="keyword">const</span><span class="special">&</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">if</span> <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="special">**</span><span class="keyword">this</span><span class="special">;</span> <span class="keyword">else</span> <span class="keyword">return</span>
+ <span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">);</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> If <code class="computeroutput"><span class="identifier">T</span></code>
+ is not <a href="../../../../../../utility/CopyConstructible.html" target="_top"><code class="computeroutput"><span class="identifier">CopyConstructible</span></code></a> or <code class="computeroutput"><span class="identifier">U</span> <span class="special">&&</span></code>
+ is not convertible to <code class="computeroutput"><span class="identifier">T</span></code>,
+ the program is ill-formed.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ ref-qualifiers on member functions this overload is replaced with the
+ <code class="computeroutput"><span class="keyword">const</span></code>-qualified member
+ function. On compilers without rvalue reference support the type of
+ <code class="computeroutput"><span class="identifier">v</span></code> becomes <code class="computeroutput"><span class="identifier">U</span> <span class="keyword">const</span><span class="special">&</span></code>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_value_or_move"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or</span><span class="special">(</span><span class="identifier">U</span> <span class="special">&&</span>
+ <span class="identifier">v</span><span class="special">)</span>
+ <span class="special">&&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> Equivalent to <code class="computeroutput"><span class="keyword">if</span> <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(**</span><span class="keyword">this</span><span class="special">);</span> <span class="keyword">else</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special"><</span><span class="identifier">U</span><span class="special">>(</span><span class="identifier">v</span><span class="special">);</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Remarks:</strong></span> If <code class="computeroutput"><span class="identifier">T</span></code>
+ is not <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>
+ or <code class="computeroutput"><span class="identifier">U</span> <span class="special">&&</span></code>
+ is not convertible to <code class="computeroutput"><span class="identifier">T</span></code>,
+ the program is ill-formed.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ ref-qualifiers on member functions this overload is not present.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_value_or_call"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">F</span> <span class="identifier">f</span><span class="special">)</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ is <a href="../../../../../../utility/CopyConstructible.html" target="_top"><code class="computeroutput"><span class="identifier">CopyConstructible</span></code></a> and <code class="computeroutput"><span class="identifier">F</span></code> models a <a href="http://www.sgi.com/tech/stl/Generator.html" target="_top"><code class="computeroutput"><span class="identifier">Generator</span></code></a> whose result type
+ is convertible to <code class="computeroutput"><span class="identifier">T</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> <code class="computeroutput"><span class="keyword">if</span>
+ <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="special">**</span><span class="keyword">this</span><span class="special">;</span> <span class="keyword">else</span> <span class="keyword">return</span> <span class="identifier">f</span><span class="special">();</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ ref-qualifiers on member functions this overload is replaced with the
+ <code class="computeroutput"><span class="keyword">const</span></code>-qualified member
+ function.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">complain_and_0</span><span class="special">()</span>
+<span class="special">{</span>
+ <span class="identifier">clog</span> <span class="special"><<</span> <span class="string">"no value returned, using default"</span> <span class="special"><<</span> <span class="identifier">endl</span><span class="special">;</span>
+ <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
+<span class="special">}</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">o1</span> <span class="special">=</span> <span class="number">1</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">oN</span> <span class="special">=</span> <span class="identifier">none</span><span class="special">;</span>
+
+<span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="identifier">o1</span><span class="special">.</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">complain_and_0</span><span class="special">);</span> <span class="comment">// fun not called</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">i</span> <span class="special">==</span> <span class="number">1</span><span class="special">);</span>
+
+<span class="keyword">int</span> <span class="identifier">j</span> <span class="special">=</span> <span class="identifier">oN</span><span class="special">.</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">complain_and_0</span><span class="special">);</span> <span class="comment">// fun called</span>
+<span class="identifier">assert</span> <span class="special">(</span><span class="identifier">i</span> <span class="special">==</span> <span class="number">0</span><span class="special">);</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_value_or_call_move"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_or_eval</span><span class="special">(</span><span class="identifier">F</span> <span class="identifier">f</span><span class="special">)</span> <span class="special">&&</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ is <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>
+ and <code class="computeroutput"><span class="identifier">F</span></code> models a <a href="http://www.sgi.com/tech/stl/Generator.html" target="_top"><code class="computeroutput"><span class="identifier">Generator</span></code></a>
+ whose result type is convertible to <code class="computeroutput"><span class="identifier">T</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> <code class="computeroutput"><span class="keyword">if</span>
+ <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(**</span><span class="keyword">this</span><span class="special">);</span> <span class="keyword">else</span> <span class="keyword">return</span>
+ <span class="identifier">f</span><span class="special">();</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ ref-qualifiers on member functions this overload is not present.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_map"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="keyword">auto</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">map</span><span class="special">(</span><span class="identifier">F</span> <span class="identifier">f</span><span class="special">)</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">-></span>
+ </code><span class="emphasis"><em>see below</em></span><code class="computeroutput"> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="keyword">auto</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">map</span><span class="special">(</span><span class="identifier">F</span> <span class="identifier">f</span><span class="special">)</span> <span class="special">&</span> <span class="special">-></span> </code><span class="emphasis"><em>see below</em></span><code class="computeroutput">
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> <code class="computeroutput"><span class="keyword">if</span>
+ <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="identifier">f</span><span class="special">(**</span><span class="keyword">this</span><span class="special">);</span> <span class="keyword">else</span> <span class="keyword">return</span>
+ <span class="identifier">none</span><span class="special">;</span></code>
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The return type of these overloads
+ is <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">decltype</span><span class="special">(</span><span class="identifier">f</span><span class="special">(**</span><span class="keyword">this</span><span class="special">))></span></code>.
+ On compilers that do not support ref-qualifiers on member functions,
+ these two (as well as the next one) overloads are replaced with good
+ old const and non-const overloads.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">auto</span> <span class="identifier">length</span> <span class="special">=</span> <span class="special">[](</span><span class="keyword">const</span> <span class="identifier">string</span><span class="special">&</span> <span class="identifier">s</span><span class="special">){</span> <span class="keyword">return</span> <span class="identifier">s</span><span class="special">.</span><span class="identifier">size</span><span class="special">();</span> <span class="special">};</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">string</span><span class="special">></span> <span class="identifier">o1</span> <span class="special">{},</span> <span class="identifier">o2</span> <span class="special">{</span><span class="string">"cat"</span><span class="special">};</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">size_t</span><span class="special">></span> <span class="identifier">os1</span> <span class="special">=</span> <span class="identifier">o1</span><span class="special">.</span><span class="identifier">map</span><span class="special">(</span><span class="identifier">length</span><span class="special">),</span> <span class="identifier">os2</span> <span class="special">=</span> <span class="identifier">o2</span><span class="special">.</span><span class="identifier">map</span><span class="special">(</span><span class="identifier">length</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">os1</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">os2</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">os2</span> <span class="special">==</span> <span class="number">3</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_map_move"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="keyword">auto</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">map</span><span class="special">(</span><span class="identifier">F</span> <span class="identifier">f</span><span class="special">)</span> <span class="special">&&</span>
+ <span class="special">-></span> </code><span class="emphasis"><em>see below</em></span><code class="computeroutput">
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> <code class="computeroutput"><span class="keyword">if</span>
+ <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="identifier">f</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(**</span><span class="keyword">this</span><span class="special">));</span> <span class="keyword">else</span> <span class="keyword">return</span>
+ <span class="identifier">none</span><span class="special">;</span></code>
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The return type of this overload
+ is <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">decltype</span><span class="special">(</span><span class="identifier">f</span><span class="special">(</span><span class="identifier">istd</span><span class="special">::</span><span class="identifier">move</span><span class="special">(**</span><span class="keyword">this</span><span class="special">)))></span></code>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_flat_map"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="keyword">auto</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">flat_map</span><span class="special">(</span><span class="identifier">F</span> <span class="identifier">f</span><span class="special">)</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">-></span>
+ </code><span class="emphasis"><em>see below</em></span><code class="computeroutput"> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="keyword">auto</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">flat_map</span><span class="special">(</span><span class="identifier">F</span> <span class="identifier">f</span><span class="special">)</span> <span class="special">&</span> <span class="special">-></span> </code><span class="emphasis"><em>see below</em></span><code class="computeroutput">
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> The return type of expression
+ <code class="computeroutput"><span class="identifier">f</span><span class="special">(**</span><span class="keyword">this</span><span class="special">)</span></code>
+ is <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span></code>
+ for some object or reference type <code class="computeroutput"><span class="identifier">U</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> <code class="computeroutput"><span class="keyword">if</span>
+ <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="identifier">f</span><span class="special">(**</span><span class="keyword">this</span><span class="special">);</span> <span class="keyword">else</span> <span class="keyword">return</span>
+ <span class="identifier">none</span><span class="special">;</span></code>
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The return type of these overloads
+ is <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span></code>.
+ On compilers that do not support ref-qualifiers on member functions,
+ these two (as well as the next one) overloads are replaced with good
+ old const and non-const overloads.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="keyword">char</span><span class="special">></span> <span class="identifier">first_char</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">string</span><span class="special">&</span> <span class="identifier">s</span><span class="special">)</span> <span class="special">{</span>
+ <span class="keyword">return</span> <span class="identifier">s</span><span class="special">.</span><span class="identifier">empty</span><span class="special">()</span> <span class="special">?</span> <span class="identifier">none</span> <span class="special">:</span> <span class="identifier">optional</span><span class="special"><</span><span class="keyword">char</span><span class="special">>(</span><span class="identifier">s</span><span class="special">[</span><span class="number">0</span><span class="special">]);</span>
+<span class="special">};</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">string</span><span class="special">></span> <span class="identifier">o1</span> <span class="special">{},</span> <span class="identifier">o2</span> <span class="special">{</span><span class="string">"cat"</span><span class="special">};</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="keyword">char</span><span class="special">></span> <span class="identifier">os1</span> <span class="special">=</span> <span class="identifier">o1</span><span class="special">.</span><span class="identifier">flat_map</span><span class="special">(</span><span class="identifier">first_char</span><span class="special">),</span> <span class="identifier">os2</span> <span class="special">=</span> <span class="identifier">o2</span><span class="special">.</span><span class="identifier">flat_map</span><span class="special">(</span><span class="identifier">first_char</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">os1</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">os2</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">*</span><span class="identifier">os2</span> <span class="special">==</span> <span class="char">'c'</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </li>
+</ul></div>
+<a name="reference_optional_flat_map_move"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="keyword">auto</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">flat_map</span><span class="special">(</span><span class="identifier">F</span> <span class="identifier">f</span><span class="special">)</span> <span class="special">&&</span>
+ <span class="special">-></span> </code><span class="emphasis"><em>see below</em></span><code class="computeroutput">
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> The return type of expression
+ <code class="computeroutput"><span class="identifier">f</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(**</span><span class="keyword">this</span><span class="special">))</span></code>
+ is <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span></code>
+ for some object or reference type <code class="computeroutput"><span class="identifier">U</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effects:</strong></span> <code class="computeroutput"><span class="keyword">if</span>
+ <span class="special">(*</span><span class="keyword">this</span><span class="special">)</span> <span class="keyword">return</span> <span class="identifier">f</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">move</span><span class="special">(**</span><span class="keyword">this</span><span class="special">));</span> <span class="keyword">else</span> <span class="keyword">return</span>
+ <span class="identifier">none</span><span class="special">;</span></code>
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The return type of this overload
+ is <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span></code>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_get_value_or_value"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">get_value_or</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="keyword">default</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">get_value_or</span><span class="special">(</span>
+ <span class="identifier">T</span><span class="special">&</span>
+ <span class="keyword">default</span> <span class="special">)</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Deprecated:</strong></span> Use <code class="computeroutput"><span class="identifier">value_or</span><span class="special">()</span></code> instead.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> A reference to the contained
+ value, if any, or <code class="computeroutput"><span class="keyword">default</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">,</span> <span class="identifier">z</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span><span class="special">;</span>
+<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">y</span> <span class="special">=</span> <span class="identifier">def</span><span class="special">.</span><span class="identifier">get_value_or</span><span class="special">(</span><span class="identifier">z</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">y</span> <span class="special">==</span> <span class="identifier">z</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">);</span>
+<span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">u</span> <span class="special">=</span> <span class="identifier">opt</span><span class="special">.</span><span class="identifier">get_value_or</span><span class="special">(</span><span class="identifier">z</span><span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">u</span> <span class="special">==</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">u</span> <span class="special">!=</span> <span class="identifier">z</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_get_ptr"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">get_ptr</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">*</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">get_ptr</span><span class="special">()</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized, a pointer to the
+ contained value; else <code class="computeroutput"><span class="number">0</span></code>
+ (<span class="emphasis"><em>null</em></span>).
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The contained value is permanently
+ stored within <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code>,
+ so you should not hold nor delete this pointer
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">T</span> <span class="identifier">v</span><span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span> <span class="identifier">copt</span><span class="special">(</span><span class="identifier">v</span><span class="special">);</span>
+<span class="identifier">T</span><span class="special">*</span> <span class="identifier">p</span> <span class="special">=</span> <span class="identifier">opt</span><span class="special">.</span><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">;</span>
+<span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">cp</span> <span class="special">=</span> <span class="identifier">copt</span><span class="special">.</span><span class="identifier">get_ptr</span><span class="special">();</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">p</span> <span class="special">==</span> <span class="identifier">get_pointer</span><span class="special">(</span><span class="identifier">opt</span><span class="special">)</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">cp</span> <span class="special">==</span> <span class="identifier">get_pointer</span><span class="special">(</span><span class="identifier">copt</span><span class="special">)</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_arrow"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span>
+ <span class="special">->()</span> <span class="keyword">const</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="identifier">T</span><span class="special">*</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span> <span class="special">->()</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires: </strong></span> <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is initialized.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> A pointer to the contained
+ value.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Throws:</strong></span> Nothing.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> The requirement is asserted
+ via <code class="computeroutput"><span class="identifier">BOOST_ASSERT</span><span class="special">()</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">X</span> <span class="special">{</span> <span class="keyword">int</span> <span class="identifier">mdata</span> <span class="special">;</span> <span class="special">}</span> <span class="special">;</span>
+<span class="identifier">X</span> <span class="identifier">x</span> <span class="special">;</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">X</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span><span class="identifier">x</span><span class="special">);</span>
+<span class="identifier">opt</span><span class="special">-></span><span class="identifier">mdata</span> <span class="special">=</span> <span class="number">2</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_bool"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">explicit</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span>
+ <span class="keyword">bool</span><span class="special">()</span>
+ <span class="keyword">const</span> <span class="keyword">noexcept</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">has_value</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">!=</span> <span class="number">0</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> On compilers that do not support
+ explicit conversion operators this falls back to safe-bool idiom.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">def</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">def</span> <span class="special">==</span> <span class="number">0</span> <span class="special">);</span>
+<span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">(</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">);</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="identifier">opt</span> <span class="special">!=</span> <span class="number">0</span> <span class="special">);</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_operator_not"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">noexcept</span>
+ <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> If <code class="computeroutput"><span class="special">*</span><span class="keyword">this</span></code> is uninitialized, <code class="computeroutput"><span class="keyword">true</span></code>; else <code class="computeroutput"><span class="keyword">false</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Notes:</strong></span> This operator is provided for
+ those compilers which can't use the <span class="emphasis"><em>unspecified-bool-type
+ operator</em></span> in certain boolean contexts.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Example:</strong></span>
+<pre class="programlisting"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="identifier">opt</span> <span class="special">;</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!</span><span class="identifier">opt</span> <span class="special">);</span>
+<span class="special">*</span><span class="identifier">opt</span> <span class="special">=</span> <span class="identifier">some_T</span> <span class="special">;</span>
+
+<span class="comment">// Notice the "double-bang" idiom here.</span>
+<span class="identifier">assert</span> <span class="special">(</span> <span class="special">!!</span><span class="identifier">opt</span> <span class="special">)</span> <span class="special">;</span>
+</pre>
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span>
+ </p>
+<a name="reference_optional_is_initialized"></a><div class="blockquote"><blockquote class="blockquote"><p>
+ <code class="computeroutput"><span class="keyword">bool</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">is_initialized</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span></code>
+ </p></blockquote></div>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <span class="bold"><strong>Deprecated:</strong></span> Same as <code class="computeroutput"><span class="keyword">explicit</span> <span class="keyword">operator</span>
+ <span class="keyword">bool</span> <span class="special">()</span>
+ <span class="special">;</span></code>
+ </li></ul></div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2018 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="header_optional_optional_refs.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="detailed_semantics___optional_references.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>
diff --git a/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header__boost_optional_hpp_.html b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header__boost_optional_hpp_.html
new file mode 100644
index 0000000..8496d37
--- /dev/null
+++ b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header__boost_optional_hpp_.html
@@ -0,0 +1,47 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Header <boost/optional.hpp></title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header <boost/optional/optional.hpp>">
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+<link rel="next" href="../dependencies_and_portability.html" title="Dependencies and Portability">
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+<a accesskey="p" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../dependencies_and_portability.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.header__boost_optional_hpp_"></a><a class="link" href="header__boost_optional_hpp_.html" title="Header <boost/optional.hpp>">Header
+ <boost/optional.hpp></a>
+</h4></div></div></div>
+<p>
+ This is an alias for header <a class="link" href="../../../optional/reference/header__boost_optional_optional_hpp_.html#boost_optional.reference.header__boost_optional_optional_hpp_.header_optional_optional" title="Synopsis"><code class="computeroutput"><span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">optional</span><span class="special">/</span><span class="identifier">optional</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code></a>.
+ </p>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2016 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
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+<a accesskey="p" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../dependencies_and_portability.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
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diff --git a/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_in_place_init.html b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_in_place_init.html
new file mode 100644
index 0000000..be67b67
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+++ b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_in_place_init.html
@@ -0,0 +1,61 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Initialization tags</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header <boost/optional/optional.hpp>">
+<link rel="prev" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header <boost/optional/optional.hpp>">
+<link rel="next" href="header_optional_optional_values.html" title="Optional Values">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
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+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header_optional_optional_values.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.header_optional_in_place_init"></a><a class="link" href="header_optional_in_place_init.html" title="Initialization tags">Initialization
+ tags</a>
+</h4></div></div></div>
+<a name="reference_in_place_init"></a><a name="reference_in_place_init_if"></a><pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span>
+
+<span class="keyword">class</span> <span class="identifier">in_place_init_t</span> <span class="special">{</span> <span class="comment">/* see below */</span> <span class="special">}</span> <span class="special">;</span>
+<span class="keyword">const</span> <span class="identifier">in_place_init_t</span> <span class="identifier">in_place_init</span> <span class="special">(</span> <span class="comment">/* see below */</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="keyword">class</span> <span class="identifier">in_place_init_if_t</span> <span class="special">{</span> <span class="comment">/*see below*/</span> <span class="special">}</span> <span class="special">;</span>
+<span class="keyword">const</span> <span class="identifier">in_place_init_if_t</span> <span class="identifier">in_place_init_if</span> <span class="special">(</span> <span class="comment">/*see below*/</span> <span class="special">)</span> <span class="special">;</span>
+
+<span class="special">}</span>
+</pre>
+<p>
+ Classes <code class="computeroutput"><span class="identifier">in_place_init_t</span></code>
+ and <code class="computeroutput"><span class="identifier">in_place_init_if_t</span></code>
+ are empty clsses. Their purpose is to control overload resolution in the
+ initialization of optional objects. They are empty, trivially copyable
+ classes with disabled default constructor.
+ </p>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2018 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header_optional_optional_values.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>
diff --git a/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_refs.html b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_refs.html
new file mode 100644
index 0000000..43b0c0a
--- /dev/null
+++ b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_refs.html
@@ -0,0 +1,119 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Optional References</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header <boost/optional/optional.hpp>">
+<link rel="prev" href="header_optional_optional_values.html" title="Optional Values">
+<link rel="next" href="detailed_semantics___optional_values.html" title="Detailed Semantics - Optional Values">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
+<td align="center"><a href="../../../../../../../index.html">Home</a></td>
+<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td>
+<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="header_optional_optional_values.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="detailed_semantics___optional_values.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.header_optional_optional_refs"></a><a class="link" href="header_optional_optional_refs.html" title="Optional References">Optional
+ References</a>
+</h4></div></div></div>
+<a name="reference_operator_template_spec"></a><pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span>
+<span class="keyword">class</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span> <span class="comment">// specilization for lvalue references</span>
+<span class="special">{</span>
+<span class="keyword">public</span> <span class="special">:</span>
+
+ <span class="keyword">typedef</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">value_type</span><span class="special">;</span>
+ <span class="keyword">typedef</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">reference_type</span><span class="special">;</span>
+ <span class="keyword">typedef</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">reference_const_type</span><span class="special">;</span> <span class="comment">// no const propagation</span>
+ <span class="keyword">typedef</span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">rval_reference_type</span><span class="special">;</span>
+ <span class="keyword">typedef</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">pointer_type</span><span class="special">;</span>
+ <span class="keyword">typedef</span> <span class="identifier">T</span><span class="special">*</span> <span class="identifier">pointer_const_type</span><span class="special">;</span> <span class="comment">// no const propagation</span>
+
+ <span class="identifier">optional</span> <span class="special">()</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_default_ctor"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_default_ctor"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">></span> <span class="identifier">optional</span><span class="special">(</span><span class="identifier">R</span><span class="special">&&</span> <span class="identifier">r</span><span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_value_ctor"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">></span> <span class="identifier">optional</span><span class="special">(</span><span class="keyword">bool</span> <span class="identifier">cond</span><span class="special">,</span> <span class="identifier">R</span><span class="special">&&</span> <span class="identifier">r</span><span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_cond_value_ctor"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_copy_ctor"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">&></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_ctor_from_opt_U"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_assign_none_t"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_copy_assign"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">&></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_assign_optional_U"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span><span class="identifier">R</span><span class="special">&&</span> <span class="identifier">r</span><span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_assign_R"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">></span> <span class="keyword">void</span> <span class="identifier">emplace</span> <span class="special">(</span> <span class="identifier">R</span><span class="special">&&</span> <span class="identifier">r</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_emplace_R"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_get"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+ <span class="identifier">T</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">*()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_get"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">T</span><span class="special">*</span> <span class="keyword">operator</span> <span class="special">->()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_arrow"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">T</span><span class="special">&</span> <span class="identifier">value</span><span class="special">()</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">></span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">value_or</span><span class="special">(</span> <span class="identifier">R</span> <span class="special">&&</span> <span class="identifier">r</span> <span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_value_or"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">value_or_eval</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_value_or_eval"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="keyword">auto</span> <span class="identifier">map</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="keyword">const</span> <span class="special">-></span> <span class="emphasis"><em>see below</em></span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_map"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="keyword">auto</span> <span class="identifier">flat_map</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="keyword">const</span> <span class="special">-></span> <span class="emphasis"><em>see below</em></span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_flat_map"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">T</span><span class="special">*</span> <span class="identifier">get_ptr</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_get_ptr"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">bool</span> <span class="identifier">has_value</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_operator_bool"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">explicit</span> <span class="keyword">operator</span> <span class="keyword">bool</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_operator_bool"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_operator_not"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="comment">// deprecated methods</span>
+
+ <span class="comment">// (deprecated)</span>
+ <span class="keyword">void</span> <span class="identifier">reset</span><span class="special">()</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_reset"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="comment">// (deprecated)</span>
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">></span> <span class="keyword">void</span> <span class="identifier">reset</span> <span class="special">(</span> <span class="identifier">R</span> <span class="special">&&</span> <span class="identifier">r</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_reset_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="comment">// (deprecated)</span>
+ <span class="keyword">bool</span> <span class="identifier">is_initialized</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_is_initialized"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="comment">// (deprecated)</span>
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">></span> <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get_value_or</span><span class="special">(</span> <span class="identifier">R</span> <span class="special">&&</span> <span class="identifier">r</span> <span class="special">)</span> <span class="identifier">constnoexcept</span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_references.html#reference_optional_ref_get_value_or_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+<span class="keyword">private</span><span class="special">:</span>
+ <span class="identifier">T</span><span class="special">*</span> <span class="identifier">ref</span><span class="special">;</span> <span class="comment">// exposition only</span>
+<span class="special">};</span>
+</pre>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2018 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="header_optional_optional_values.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="detailed_semantics___optional_values.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>
diff --git a/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_values.html b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_values.html
new file mode 100644
index 0000000..5e1edff
--- /dev/null
+++ b/doc/html/boost_optional/reference/header__boost_optional_optional_hpp_/header_optional_optional_values.html
@@ -0,0 +1,154 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Optional Values</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../../../optional/reference/header__boost_optional_optional_hpp_.html" title="Header <boost/optional/optional.hpp>">
+<link rel="prev" href="header_optional_in_place_init.html" title="Initialization tags">
+<link rel="next" href="header_optional_optional_refs.html" title="Optional References">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td>
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+<a name="boost_optional.reference.header__boost_optional_optional_hpp_.header_optional_optional_values"></a><a class="link" href="header_optional_optional_values.html" title="Optional Values">Optional
+ Values</a>
+</h4></div></div></div>
+<a name="reference_operator_template"></a><pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span>
+<span class="keyword">class</span> <span class="identifier">optional</span>
+<span class="special">{</span>
+<span class="keyword">public</span> <span class="special">:</span>
+
+ <span class="keyword">typedef</span> <span class="identifier">T</span> <span class="identifier">value_type</span> <span class="special">;</span>
+ <span class="keyword">typedef</span> <span class="identifier">T</span> <span class="special">&</span> <span class="identifier">reference_type</span> <span class="special">;</span>
+ <span class="keyword">typedef</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">reference_const_type</span> <span class="special">;</span>
+ <span class="keyword">typedef</span> <span class="identifier">T</span> <span class="special">&&</span> <span class="identifier">rval_reference_type</span> <span class="special">;</span>
+ <span class="keyword">typedef</span> <span class="identifier">T</span> <span class="special">*</span> <span class="identifier">pointer_type</span> <span class="special">;</span>
+ <span class="keyword">typedef</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">pointer_const_type</span> <span class="special">;</span>
+
+ <span class="identifier">optional</span> <span class="special">()</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_none_t"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_move_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">optional</span> <span class="special">(</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_bool_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span><span class="emphasis"><em>see below</em></span><span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_move_constructor_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_other_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">>&&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_move_constructor_other_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">in_place_init_t</span><span class="special">,</span> <span class="identifier">Args</span><span class="special">&&...</span> <span class="identifier">args</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_in_place_init"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">in_place_init_if_t</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">condition</span><span class="special">,</span> <span class="identifier">Args</span><span class="special">&&...</span> <span class="identifier">args</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_in_place_init_if"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">InPlaceFactory</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">InPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_factory"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">TypedInPlaceFactory</span><span class="special">></span> <span class="keyword">explicit</span> <span class="identifier">optional</span> <span class="special">(</span> <span class="identifier">TypedInPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_constructor_factory"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">none_t</span> <span class="special">)</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_equal_none_t"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_equal_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_move_equal_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_equal_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special">&&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="keyword">noexcept</span><span class="special">(</span><span class="emphasis"><em>see below</em></span><span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_move_equal_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_equal_other_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">>&&</span> <span class="identifier">rhs</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_move_equal_other_optional"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">></span> <span class="keyword">void</span> <span class="identifier">emplace</span> <span class="special">(</span> <span class="identifier">Args</span><span class="special">&&...</span> <span class="identifier">args</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_emplace"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">InPlaceFactory</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">InPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_equal_factory"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">TypedInPlaceFactory</span><span class="special">></span> <span class="identifier">optional</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">=</span> <span class="special">(</span> <span class="identifier">TypedInPlaceFactory</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_equal_factory"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">get</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_get"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+ <span class="identifier">T</span><span class="special">&</span> <span class="identifier">get</span><span class="special">()</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_get"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="keyword">operator</span> <span class="special">->()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_arrow"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+ <span class="identifier">T</span><span class="special">*</span> <span class="keyword">operator</span> <span class="special">->()</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_arrow"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">*()</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_asterisk"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+ <span class="identifier">T</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">*()</span> <span class="special">&</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_asterisk"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+ <span class="identifier">T</span><span class="special">&&</span> <span class="keyword">operator</span> <span class="special">*()</span> <span class="special">&&</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_asterisk_move"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">value</span><span class="special">()</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+ <span class="identifier">T</span><span class="special">&</span> <span class="identifier">value</span><span class="special">()</span> <span class="special">&</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+ <span class="identifier">T</span><span class="special">&&</span> <span class="identifier">value</span><span class="special">()</span> <span class="special">&&</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_value_move"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">value_or</span><span class="special">(</span> <span class="identifier">U</span> <span class="special">&&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_value_or"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">U</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">value_or</span><span class="special">(</span> <span class="identifier">U</span> <span class="special">&&</span> <span class="identifier">v</span> <span class="special">)</span> <span class="special">&&</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_value_or_move"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">value_or_eval</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_value_or_call"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="identifier">T</span> <span class="identifier">value_or_eval</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">&&</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_value_or_call_move"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="keyword">auto</span> <span class="identifier">map</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">-></span> <span class="emphasis"><em>see below</em></span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_map"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="keyword">auto</span> <span class="identifier">map</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">&</span> <span class="special">-></span> <span class="emphasis"><em>see below</em></span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_map"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="keyword">auto</span> <span class="identifier">map</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">&&</span> <span class="special">-></span> <span class="emphasis"><em>see below</em></span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_map_move"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="keyword">auto</span> <span class="identifier">flat_map</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">-></span> <span class="emphasis"><em>see below</em></span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_flat_map"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="keyword">auto</span> <span class="identifier">flat_map</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">&</span> <span class="special">-></span> <span class="emphasis"><em>see below</em></span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_flat_map"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+ <span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">F</span><span class="special">></span> <span class="keyword">auto</span> <span class="identifier">flat_map</span><span class="special">(</span> <span class="identifier">F</span> <span class="identifier">f</span> <span class="special">)</span> <span class="special">&&</span> <span class="special">-></span> <span class="emphasis"><em>see below</em></span><span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_flat_map_move"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="identifier">T</span> <span class="keyword">const</span><span class="special">*</span> <span class="identifier">get_ptr</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_get_ptr"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+ <span class="identifier">T</span><span class="special">*</span> <span class="identifier">get_ptr</span><span class="special">()</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_get_ptr"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">bool</span> <span class="identifier">has_value</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_bool"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">explicit</span> <span class="keyword">operator</span> <span class="keyword">bool</span><span class="special">()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_bool"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!()</span> <span class="keyword">const</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_operator_not"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="comment">// deprecated methods</span>
+
+ <span class="comment">// (deprecated)</span>
+ <span class="keyword">void</span> <span class="identifier">reset</span><span class="special">()</span> <span class="keyword">noexcept</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_reset"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="comment">// (deprecated)</span>
+ <span class="keyword">void</span> <span class="identifier">reset</span> <span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="special">)</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_reset_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="comment">// (deprecated)</span>
+ <span class="keyword">bool</span> <span class="identifier">is_initialized</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_is_initialized"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="comment">// (deprecated)</span>
+ <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">get_value_or</span><span class="special">(</span> <span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="keyword">default</span> <span class="special">)</span> <span class="keyword">const</span> <span class="special">;</span> <a class="link" href="detailed_semantics___optional_values.html#reference_optional_get_value_or_value"><span class="inlinemediaobject"><img src="../../../images/callouts/R.png" alt="R"></span></a>
+<span class="special">};</span>
+</pre>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2018 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="header_optional_in_place_init.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../optional/reference/header__boost_optional_optional_hpp_.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="header_optional_optional_refs.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>
diff --git a/doc/html/boost_optional/reference/io_header.html b/doc/html/boost_optional/reference/io_header.html
new file mode 100644
index 0000000..fd8599f
--- /dev/null
+++ b/doc/html/boost_optional/reference/io_header.html
@@ -0,0 +1,72 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Header <boost/optional/optional_io.hpp></title>
+<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
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+<link rel="next" href="io_header/io_semantics.html" title="Detailed semantics">
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+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
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+<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td>
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+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="header__boost_optional_bad_optional_access_hpp_/detailed_semantics.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="io_header/io_semantics.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h3 class="title">
+<a name="boost_optional.reference.io_header"></a><a class="link" href="io_header.html" title="Header <boost/optional/optional_io.hpp>">Header <boost/optional/optional_io.hpp></a>
+</h3></div></div></div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.io_header.io_synop"></a><a class="link" href="io_header.html#boost_optional.reference.io_header.io_synop" title="Synopsis">Synopsis</a>
+</h4></div></div></div>
+<p>
+</p>
+<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">istream</span><span class="special">></span>
+<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">ostream</span><span class="special">></span>
+<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">optional</span><span class="special">/</span><span class="identifier">optional</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
+
+<span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span>
+
+<span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">CharType</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">CharTrait</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span>
+ <span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special"><</span><span class="identifier">CharType</span><span class="special">,</span> <span class="identifier">CharTrait</span><span class="special">>&</span>
+ <span class="keyword">operator</span><span class="special"><<(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special"><</span><span class="identifier">CharType</span><span class="special">,</span> <span class="identifier">CharTrait</span><span class="special">>&</span> <span class="identifier">out</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span><span class="special">);</span> <a class="link" href="io_header/io_semantics.html#reference_operator_ostream"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+
+ <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">CharType</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">CharTrait</span><span class="special">></span>
+ <span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special"><</span><span class="identifier">CharType</span><span class="special">,</span> <span class="identifier">CharTrait</span><span class="special">>&</span>
+ <span class="keyword">operator</span><span class="special"><<(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special"><</span><span class="identifier">CharType</span><span class="special">,</span> <span class="identifier">CharTrait</span><span class="special">>&</span> <span class="identifier">out</span><span class="special">,</span> <span class="identifier">none_t</span> <span class="keyword">const</span><span class="special">&);</span> <a class="link" href="io_header/io_semantics.html#reference_operator_ostream_none"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+
+<span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">CharType</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">CharTrait</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span>
+ <span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_istream</span><span class="special"><</span><span class="identifier">CharType</span><span class="special">,</span> <span class="identifier">CharTrait</span><span class="special">>&</span>
+ <span class="keyword">operator</span><span class="special">>>(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_istream</span><span class="special"><</span><span class="identifier">CharType</span><span class="special">,</span> <span class="identifier">CharTrait</span><span class="special">>&</span> <span class="identifier">in</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">v</span><span class="special">);</span> <a class="link" href="io_header/io_semantics.html#reference_operator_istream"><span class="inlinemediaobject"><img src="../../images/callouts/R.png" alt="R"></span></a>
+
+<span class="special">}</span> <span class="comment">// namespace boost</span>
+</pre>
+<p>
+ </p>
+</div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2018 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="header__boost_optional_bad_optional_access_hpp_/detailed_semantics.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="io_header/io_semantics.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+</body>
+</html>
diff --git a/doc/html/boost_optional/reference/io_header/io_semantics.html b/doc/html/boost_optional/reference/io_header/io_semantics.html
new file mode 100644
index 0000000..2e8ed56
--- /dev/null
+++ b/doc/html/boost_optional/reference/io_header/io_semantics.html
@@ -0,0 +1,112 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Detailed semantics</title>
+<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets Vsnapshot">
+<link rel="home" href="../../../index.html" title="Boost.Optional">
+<link rel="up" href="../io_header.html" title="Header <boost/optional/optional_io.hpp>">
+<link rel="prev" href="../io_header.html" title="Header <boost/optional/optional_io.hpp>">
+<link rel="next" href="../header__boost_optional_optional_fwd_hpp_.html" title="Header <boost/optional/optional_fwd.hpp>">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
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+</tr></table>
+<hr>
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+<a accesskey="p" href="../io_header.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../io_header.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../header__boost_optional_optional_fwd_hpp_.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h4 class="title">
+<a name="boost_optional.reference.io_header.io_semantics"></a><a class="link" href="io_semantics.html" title="Detailed semantics">Detailed
+ semantics</a>
+</h4></div></div></div>
+<p>
+ <a name="reference_operator_ostream"></a><code class="computeroutput"><span class="keyword">template</span>
+ <span class="special"><</span><span class="keyword">class</span>
+ <span class="identifier">CharType</span><span class="special">,</span>
+ <span class="keyword">class</span> <span class="identifier">CharTrait</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span></code>
+ <br>     <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special"><</span><span class="identifier">CharType</span><span class="special">,</span> <span class="identifier">CharTrait</span><span class="special">>&</span></code> <br>     <code class="computeroutput"><span class="keyword">operator</span><span class="special"><<(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special"><</span><span class="identifier">CharType</span><span class="special">,</span> <span class="identifier">CharTrait</span><span class="special">>&</span>
+ <span class="identifier">out</span><span class="special">,</span>
+ <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span><span class="special">);</span></code>
+ </p>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Outputs an implementation-defined
+ string. The output contains the information about whether the optional
+ object contains a value or not. If <code class="computeroutput"><span class="identifier">v</span></code>
+ contains a value, the output contains result of calling <code class="computeroutput"><span class="identifier">out</span> <span class="special"><<</span>
+ <span class="special">*</span><span class="identifier">v</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="identifier">out</span></code>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> <a name="reference_operator_ostream_none"></a>
+ </p>
+<p>
+ <code class="computeroutput"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">CharType</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">CharTrait</span><span class="special">,</span>
+ <span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span></code> <br>     <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special"><</span><span class="identifier">CharType</span><span class="special">,</span> <span class="identifier">CharTrait</span><span class="special">>&</span></code>
+ <br>     <code class="computeroutput"><span class="keyword">operator</span><span class="special"><<(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special"><</span><span class="identifier">CharType</span><span class="special">,</span> <span class="identifier">CharTrait</span><span class="special">>&</span> <span class="identifier">out</span><span class="special">,</span> <span class="identifier">none_t</span><span class="special">);</span></code>
+ </p>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Outputs an implementation-defined
+ string.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="identifier">out</span></code>.
+ </li>
+</ul></div>
+<p>
+ <span class="inlinemediaobject"><img src="../../../images/space.png" alt="space"></span> <a name="reference_operator_istream"></a>
+ </p>
+<p>
+ <code class="computeroutput"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">CharType</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">CharTrait</span><span class="special">,</span>
+ <span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span></code> <br>     <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special"><</span><span class="identifier">CharType</span><span class="special">,</span> <span class="identifier">CharTrait</span><span class="special">>&</span></code>
+ <br>     <code class="computeroutput"><span class="keyword">operator</span><span class="special">>>(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_istream</span><span class="special"><</span><span class="identifier">CharType</span><span class="special">,</span> <span class="identifier">CharTrait</span><span class="special">>&</span> <span class="identifier">in</span><span class="special">,</span> <span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">>&</span> <span class="identifier">v</span><span class="special">);</span></code>
+ </p>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <span class="bold"><strong>Requires:</strong></span> <code class="computeroutput"><span class="identifier">T</span></code>
+ is <a href="http://www.sgi.com/tech/stl/DefaultConstructible.html" target="_top"><code class="computeroutput"><span class="identifier">DefaultConstructible</span></code></a> and
+ <code class="computeroutput"><span class="identifier">MoveConstructible</span></code>.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Effect:</strong></span> Reads the value of optional
+ object from <code class="computeroutput"><span class="identifier">in</span></code>. If
+ the string representation indicates that the optional object should
+ contain a value, <code class="computeroutput"><span class="identifier">v</span></code>
+ contains a value and its contained value is obtained as if by default-constructing
+ an object <code class="computeroutput"><span class="identifier">o</span></code> of type
+ <code class="computeroutput"><span class="identifier">T</span></code> and then calling
+ <code class="computeroutput"><span class="identifier">in</span> <span class="special">>></span>
+ <span class="identifier">o</span></code>; otherwise <code class="computeroutput"><span class="identifier">v</span></code> does not contain a value, and the
+ previously contained value (if any) has been destroyed.
+ </li>
+<li class="listitem">
+ <span class="bold"><strong>Returns:</strong></span> <code class="computeroutput"><span class="identifier">out</span></code>.
+ </li>
+</ul></div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2018 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="../io_header.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../io_header.html"><img src="../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../header__boost_optional_optional_fwd_hpp_.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a>
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diff --git a/doc/html/boost_optional/reference/relnotes.html b/doc/html/boost_optional/reference/relnotes.html
new file mode 100644
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+++ b/doc/html/boost_optional/reference/relnotes.html
@@ -0,0 +1,183 @@
+<html>
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
+<title>Release Notes</title>
+<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css">
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+<link rel="home" href="../../index.html" title="Boost.Optional">
+<link rel="up" href="../../optional/reference.html" title="Reference">
+<link rel="prev" href="dependencies_and_portability/optional_reference_binding.html" title="Optional Reference Binding">
+<link rel="next" href="acknowledgements.html" title="Acknowledgements">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
+<table cellpadding="2" width="100%"><tr>
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+<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
+<td align="center"><a href="../../../../../../more/index.htm">More</a></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="dependencies_and_portability/optional_reference_binding.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="acknowledgements.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
+</div>
+<div class="section">
+<div class="titlepage"><div><div><h3 class="title">
+<a name="boost_optional.reference.relnotes"></a><a class="link" href="relnotes.html" title="Release Notes">Release Notes</a>
+</h3></div></div></div>
+<h5>
+<a name="boost_optional.reference.relnotes.h0"></a>
+ <span class="phrase"><a name="boost_optional.reference.relnotes.boost_release_x_xx"></a></span><a class="link" href="relnotes.html#boost_optional.reference.relnotes.boost_release_x_xx">Boost Release
+ X.XX</a>
+ </h5>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ Now <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span></code> is specialized for reference
+ parameters. This way the <code class="computeroutput"><span class="keyword">sizeof</span></code>
+ of optional reference is that of a pointer, and a number of bugs is avoided.
+ </li></ul></div>
+<h5>
+<a name="boost_optional.reference.relnotes.h1"></a>
+ <span class="phrase"><a name="boost_optional.reference.relnotes.boost_release_1_60"></a></span><a class="link" href="relnotes.html#boost_optional.reference.relnotes.boost_release_1_60">Boost Release
+ 1.60</a>
+ </h5>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ Changed the implementation of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none</span></code>
+ again. Now it is a const object with internal linkage (as any other tag).
+ This fixes <a href="https://svn.boost.org/trac/boost/ticket/11203" target="_top">Trac
+ #11203</a>.
+ </li></ul></div>
+<h5>
+<a name="boost_optional.reference.relnotes.h2"></a>
+ <span class="phrase"><a name="boost_optional.reference.relnotes.boost_release_1_59"></a></span><a class="link" href="relnotes.html#boost_optional.reference.relnotes.boost_release_1_59">Boost Release
+ 1.59</a>
+ </h5>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ For C++03 compilers, added 0-argument overload for member function <code class="computeroutput"><span class="identifier">emplace</span><span class="special">()</span></code>,
+ and therewith removed the dependency on <code class="computeroutput"><span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">utility</span><span class="special">/</span><span class="identifier">in_place_factory</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code>.
+ </li>
+<li class="listitem">
+ Fixed <a href="https://svn.boost.org/trac/boost/ticket/11241" target="_top">Trac
+ #11241</a>.
+ </li>
+</ul></div>
+<h5>
+<a name="boost_optional.reference.relnotes.h3"></a>
+ <span class="phrase"><a name="boost_optional.reference.relnotes.boost_release_1_58"></a></span><a class="link" href="relnotes.html#boost_optional.reference.relnotes.boost_release_1_58">Boost Release
+ 1.58</a>
+ </h5>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none_t</span></code> is no longer convertible from
+ literal <code class="computeroutput"><span class="number">0</span></code>. This avoids a
+ bug where <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">rational</span><span class="special"><</span><span class="keyword">int</span><span class="special">>></span>
+ <span class="identifier">oi</span> <span class="special">=</span>
+ <span class="number">0</span><span class="special">;</span></code>
+ would initialize an optional object with no contained value.
+ </li>
+<li class="listitem">
+ Improved the trick that prevents streaming out <code class="computeroutput"><span class="identifier">optional</span></code>
+ without header <code class="computeroutput"><span class="identifier">optional_io</span><span class="special">.</span><span class="identifier">hpp</span></code>
+ by using safe-bool idiom. This addresses <a href="https://svn.boost.org/trac/boost/ticket/10825" target="_top">Trac
+ #10825</a>.
+ </li>
+<li class="listitem">
+ IOStream operators are now mentioned in documentation.
+ </li>
+<li class="listitem">
+ Added a way to manually disable move semantics: just define macro <code class="computeroutput"><span class="identifier">BOOST_OPTIONAL_CONFIG_NO_RVALUE_REFERENCES</span></code>.
+ This can be used to work around <a href="https://svn.boost.org/trac/boost/ticket/10399" target="_top">Trac
+ #10399</a>.
+ </li>
+<li class="listitem">
+ It is no longer possible to assign <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">U</span><span class="special">></span></code> to <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> when <code class="computeroutput"><span class="identifier">U</span></code>
+ is not assignable or convertible to <code class="computeroutput"><span class="identifier">T</span></code>
+ (<a href="https://svn.boost.org/trac/boost/ticket/11087" target="_top">Trac #11087</a>).
+ </li>
+<li class="listitem">
+ Value accessors now work correctly on rvalues of <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">&></span></code> (<a href="https://svn.boost.org/trac/boost/ticket/10839" target="_top">Trac
+ #10839</a>).
+ </li>
+</ul></div>
+<h5>
+<a name="boost_optional.reference.relnotes.h4"></a>
+ <span class="phrase"><a name="boost_optional.reference.relnotes.boost_release_1_57"></a></span><a class="link" href="relnotes.html#boost_optional.reference.relnotes.boost_release_1_57">Boost Release
+ 1.57</a>
+ </h5>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
+ <a href="https://github.com/boostorg/optional/pull/9" target="_top">Git pull #9</a>:
+ <span class="emphasis"><em>"Supply <code class="computeroutput"><span class="special"><</span><span class="identifier">string</span><span class="special">></span></code>
+ to fix C++03 compile error on <code class="computeroutput"><span class="identifier">logic_error</span><span class="special">(</span><span class="string">"..."</span><span class="special">)</span></code>"</em></span>.
+ </li></ul></div>
+<h5>
+<a name="boost_optional.reference.relnotes.h5"></a>
+ <span class="phrase"><a name="boost_optional.reference.relnotes.boost_release_1_56"></a></span><a class="link" href="relnotes.html#boost_optional.reference.relnotes.boost_release_1_56">Boost Release
+ 1.56</a>
+ </h5>
+<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
+<li class="listitem">
+ Added support for rvalue references. Now <code class="computeroutput"><span class="identifier">optional</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> works with moveable but non-copyable
+ <code class="computeroutput"><span class="identifier">T</span></code>'s,
+ </li>
+<li class="listitem">
+ Improved <code class="computeroutput"><span class="identifier">swap</span></code> (now uses
+ move operations),
+ </li>
+<li class="listitem">
+ Added function <code class="computeroutput"><span class="identifier">emplace</span><span class="special">()</span></code>. This is the last of the requests from
+ <a href="https://svn.boost.org/trac/boost/ticket/1841" target="_top">Trac #1841</a>,
+ </li>
+<li class="listitem">
+ <code class="computeroutput"><span class="identifier">optional</span></code> is moveable,
+ including conditional <code class="computeroutput"><span class="keyword">noexcept</span></code>
+ specifications, which make it <code class="computeroutput"><span class="identifier">move_if_noexcept</span></code>-friendly,
+ </li>
+<li class="listitem">
+ Using explicit operator bool() on platforms that support it (<a href="https://svn.boost.org/trac/boost/ticket/4227" target="_top">Trac
+ #4227</a>) (breaking change),
+ </li>
+<li class="listitem">
+ Forward declaration of <code class="computeroutput"><span class="keyword">operator</span><span class="special"><<(</span><span class="identifier">ostream</span><span class="special">&,</span> <span class="identifier">optional</span>
+ <span class="keyword">const</span><span class="special">&)</span></code>
+ to prevent inadvertent incorrect serialization of optional objects,
+ </li>
+<li class="listitem">
+ Removed deprecated function <code class="computeroutput"><span class="identifier">reset</span><span class="special">()</span></code> from examples (<a href="https://svn.boost.org/trac/boost/ticket/9005" target="_top">Trac
+ #9005</a>),
+ </li>
+<li class="listitem">
+ Equality comparison with <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">none</span></code>
+ does not require that <code class="computeroutput"><span class="identifier">T</span></code>
+ be EqualityComparable,
+ </li>
+<li class="listitem">
+ Optional rvalue references are explicitly disallowed,
+ </li>
+<li class="listitem">
+ Binding temporaries to optional references is explicitly disallowed (breaking
+ change),
+ </li>
+<li class="listitem">
+ More ways to access the contained value, functions <code class="computeroutput"><span class="identifier">value</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">value_or</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">value_or_eval</span><span class="special">()</span></code>,
+ </li>
+<li class="listitem">
+ Updated and reorganized documentation, added tutorial and quick guide
+ sections.
+ </li>
+</ul></div>
+</div>
+<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
+<td align="left"></td>
+<td align="right"><div class="copyright-footer">Copyright © 2003-2007 Fernando Luis Cacciola Carballal<br>Copyright © 2014-2016 Andrzej Krzemieński<p>
+ Distributed under the Boost Software License, Version 1.0. (See accompanying
+ file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
+ </p>
+</div></td>
+</tr></table>
+<hr>
+<div class="spirit-nav">
+<a accesskey="p" href="dependencies_and_portability/optional_reference_binding.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../optional/reference.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="acknowledgements.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a>
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+</body>
+</html>