ceph/src/boost/libs/preprocessor/doc/ref/identity.html

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   2 <head>
   3         <title>BOOST_PP_IDENTITY</title>
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   8                 The <b>BOOST_PP_IDENTITY</b> macro expands to its argument when invoked.
   9         </div>
  10         <h4>Usage</h4>
  11                 <div class="code">
  12                         <b>BOOST_PP_IDENTITY</b>(<i>item</i>)()
  13                 </div>
  14         <h4>Arguments</h4>
  15                 <dl>
  16                         <dt>item</dt>
  17                         <dd>
  18                                 The result of the expansion.
  19                         </dd>
  20                 </dl>
  21         <h4>Remarks</h4>
  22                 <div>
  23                         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.
  24                 </div>
  25         <h4>See Also</h4>
  26                 <ul>
  27                         <li><a href="if.html">BOOST_PP_IF</a></li>
  28                         <li><a href="iif.html">BOOST_PP_IIF</a></li>
  29                 </ul>
  30         <h4>Requirements</h4>
  31                 <div>
  32                         <b>Header:</b> &nbsp;<a href="../headers/facilities/identity.html">&lt;boost/preprocessor/facilities/identity.hpp&gt;</a>
  33                 </div>
  34         <h4>Sample Code</h4>
  35 <div><pre>
  36 #include &lt;<a href="../headers/control/if.html">boost/preprocessor/control/if.hpp</a>&gt;
  37 #include &lt;<a href="../headers/facilities/empty.html">boost/preprocessor/facilities/empty.hpp</a>&gt;
  38 #include &lt;<a href="../headers/facilities/identity.html">boost/preprocessor/facilities/identity.hpp</a>&gt;
  39
  40 #define MACRO(n) <a href="if.html">BOOST_PP_IF</a>(n, <a href="identity.html">BOOST_PP_IDENTITY</a>(x), <a href="empty.html">BOOST_PP_EMPTY</a>)()
  41
  42 MACRO(0) // expands to nothing
  43 MACRO(1) // expands to x
  44 </pre></div>
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  47                 <i>© Copyright <a href="http://www.housemarque.com" target="_top">Housemarque Oy</a> 2002</i>
  48                 </br><i>© Copyright Paul Mensonides 2002</i>
  49         </div>
  50         <div style="margin-left: 0px;">
  51                 <p><small>Distributed under the Boost Software License, Version 1.0. (See
  52                 accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or
  53                 copy at <a href=
  54                 "http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a>)</small></p>
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