| Brian Silverman | f27e085 | 2018-08-04 23:56:45 -0700 | [diff] [blame^] | 1 | <html> |
| 2 | <head> |
| 3 | <title>BOOST_PP_IDENTITY_N</title> |
| 4 | <link rel="stylesheet" type="text/css" href="../styles.css"> |
| 5 | </head> |
| 6 | <body> |
| 7 | <div style="margin-left: 0px;"> |
| 8 | The <b>BOOST_PP_IDENTITY_N</b> macro expands to its first argument when invoked. |
| 9 | </div> |
| 10 | <h4>Usage</h4> |
| 11 | <div class="code"> |
| 12 | <b>BOOST_PP_IDENTITY_N</b>(<i>item,n</i>)(n-arguments) |
| 13 | </div> |
| 14 | <h4>Arguments</h4> |
| 15 | <dl> |
| 16 | <dt>item</dt> |
| 17 | <dd> |
| 18 | The result of the expansion. |
| 19 | </dd> |
| 20 | <dt>n</dt> |
| 21 | <dd> |
| 22 | The number of arguments when invoked. |
| 23 | </dd> |
| 24 | </dl> |
| 25 | <h4>Remarks</h4> |
| 26 | <div> |
| 27 | This macro is designed to be used with <b>BOOST_PP_IF</b> and <b>BOOST_PP_IIF</b> when only one of the clauses needs to be invoked. |
| 28 | </div> |
| 29 | <h4>See Also</h4> |
| 30 | <ul> |
| 31 | <li><a href="if.html">BOOST_PP_IF</a></li> |
| 32 | <li><a href="iif.html">BOOST_PP_IIF</a></li> |
| 33 | </ul> |
| 34 | <h4>Requirements</h4> |
| 35 | <div> |
| 36 | <b>Header:</b> <a href="../headers/facilities/identity.html"><boost/preprocessor/facilities/identity.hpp></a> |
| 37 | </div> |
| 38 | <h4>Sample Code</h4> |
| 39 | <div><pre> |
| 40 | #include <<a href="../headers/control/if.html">boost/preprocessor/control/if.hpp</a>> |
| 41 | #include <<a href="../headers/facilities/identity.html">boost/preprocessor/facilities/identity.hpp</a>> |
| 42 | |
| 43 | #define MACRO_CAT(y,z) y ## z |
| 44 | #define MACRO(n) <a href="if.html">BOOST_PP_IF</a>(n, <a href="identity_n.html">BOOST_PP_IDENTITY_N</a>(x,2), MACRO_CAT)(a,b) |
| 45 | |
| 46 | MACRO(0) // expands to ab |
| 47 | MACRO(1) // expands to x |
| 48 | </pre></div> |
| 49 | <hr size="1"> |
| 50 | <div style="margin-left: 0px"><i>© Copyright Edward Diener 2015</i></div> |
| 51 | <div style="margin-left: 0px;"> |
| 52 | <p><small>Distributed under the Boost Software License, Version 1.0. (See |
| 53 | accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or |
| 54 | copy at <a href= |
| 55 | "http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a>)</small></p> |
| 56 | </div> |
| 57 | </body> |
| 58 | </html> |