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

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   3         <title>BOOST_PP_EMPTY</title>
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   9                 The <b>BOOST_PP_EMPTY</b> macro is a nullary utility macro that expands to nothing.
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  11         <h4>Usage</h4>
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  13                         <b>BOOST_PP_EMPTY</b>()
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  15         <h4>Remarks</h4>
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  17                         This macro is helps avoid inefficient macro-expansion.&nbsp;
  18                         It is primarily useful as arguments to <b>BOOST_PP_IF</b> or <b>BOOST_PP_IIF</b>.
  19                 </div>
  20         <h4>Requirements</h4>
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  22                         <b>Header:</b> &nbsp;<a href="../headers/facilities/empty.html">&lt;boost/preprocessor/facilities/empty.hpp&gt;</a>
  23                 </div>
  24         <h4>Sample Code</h4>
  25 <div><pre>
  26 #include &lt;<a href="../headers/control/if.html">boost/preprocessor/control/if.hpp</a>&gt;
  27 #include &lt;<a href="../headers/facilities/empty.html">boost/preprocessor/facilities/empty.hpp</a>&gt;
  28
  29 #define X() result
  30 #define MACRO(c) <a href="if.html">BOOST_PP_IF</a>(c, X, <a href="empty.html">BOOST_PP_EMPTY</a>)()
  31
  32 MACRO(0) // expands to nothing
  33 MACRO(1) // expands to result
  34 </pre></div>
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  37                 <i>© Copyright <a href="http://www.housemarque.com" target="_top">Housemarque Oy</a> 2002</i>
  38                 </br><i>© Copyright Paul Mensonides 2002</i>
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  41                 <p><small>Distributed under the Boost Software License, Version 1.0. (See
  42                 accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or
  43                 copy at <a href=
  44                 "http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a>)</small></p>
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