1<html> 2<head> 3 <title>BOOST_PP_EMPTY</title> 4 <link rel="stylesheet" type="text/css" href="../styles.css"> 5 6</head> 7<body> 8 <div style="margin-left: 0px;"> 9 The <b>BOOST_PP_EMPTY</b> macro is a nullary utility macro that expands to nothing. 10 </div> 11 <h4>Usage</h4> 12 <div class="code"> 13 <b>BOOST_PP_EMPTY</b>() 14 </div> 15 <h4>Remarks</h4> 16 <div> 17 This macro is helps avoid inefficient macro-expansion. 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> 21 <div> 22 <b>Header:</b> <a href="../headers/facilities/empty.html"><boost/preprocessor/facilities/empty.hpp></a> 23 </div> 24 <h4>Sample Code</h4> 25<div><pre> 26#include <<a href="../headers/control/if.html">boost/preprocessor/control/if.hpp</a>> 27#include <<a href="../headers/facilities/empty.html">boost/preprocessor/facilities/empty.hpp</a>> 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 32MACRO(0) // expands to nothing 33MACRO(1) // expands to result 34</pre></div> 35 <hr size="1"> 36 <div style="margin-left: 0px;"> 37 <i>� Copyright <a href="http://www.housemarque.com" target="_top">Housemarque Oy</a> 2002</i> 38 </br><i>� Copyright Paul Mensonides 2002</i> 39 </div> 40 <div style="margin-left: 0px;"> 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> 45 </div> 46</body> 47</html> 48