doc/has_trivial_assign.qbk

[/ 
  Copyright 2007 John Maddock.
  Distributed under the Boost Software License, Version 1.0.
  (See accompanying file LICENSE_1_0.txt or copy at
  http://www.boost.org/LICENSE_1_0.txt).
]

[section:has_trivial_assign has_trivial_assign]
   template <class T>
   struct has_trivial_assign : public __tof {};
  
__inherit If T is a (possibly cv-qualified) type with a trivial assignment-operator
then inherits from __true_type, otherwise inherits from __false_type.

If a type has a trivial assignment-operator then the operator has the same effect
as copying the bits of one object to the other: 
calls to the operator can be safely replaced with a call to `memcpy`.

__compat Without some (as yet unspecified) help from the compiler, 
has_trivial_assign will never report that a user-defined class or struct has a 
trivial constructor; this is always safe, if possibly sub-optimal.  In order to
correctly handle deleted or private assignment operators, the compiler must also
support C++11's `decltype`.
Currently (May 2015) compilers more recent than Visual C++ 8, GCC-4.3, Greenhills 6.0, 
Intel-11.0, and Codegear have the necessary compiler __intrinsics to ensure that this 
trait "just works".  You may also test to see if the necessary __intrinsics are available 
by checking to see if the macro `BOOST_HAS_TRIVIAL_ASSIGN` is defined.


__std_ref 12.8p11.

__header ` #include <boost/type_traits/has_trivial_assign.hpp>` or ` #include <boost/type_traits.hpp>`

__examples

[:`has_trivial_assign<int>` inherits from `__true_type`.]

[:`has_trivial_assign<char*>::type` is the type `__true_type`.]

[:`has_trivial_assign<int (*)(long)>::value` is an integral constant 
expression that evaluates to /true/.]

[:`has_trivial_assign<MyClass>::value` is an integral constant 
expression that evaluates to /false/.]

[:`has_trivial_assign<T>::value_type` is the type `bool`.]

[endsect]