1<html> 2<head> 3 <title>BOOST_PP_EXPAND</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_EXPAND</b> macro performs a double macro-expansion on its argument. 9 </div> 10 <h4>Usage</h4> 11 <div class="code"> 12 <b>BOOST_PP_EXPAND</b>(<i>x</i>) 13 </div> 14 <h4>Arguments</h4> 15 <dl> 16 <dt>x</dt> 17 <dd> 18 The argument to be expanded twice. 19 </dd> 20 </dl> 21 <h4>Remarks</h4> 22 <div> 23 This macro is useful when a delay is necessary to produce the correct semantics of a macro invocation. 24 For example, when a macro expands to an argument list to another macro. 25 This macro will expand the argument list on the first pass, and then rescan to expand any more macros. 26 </div> 27 <h4>Requirements</h4> 28 <div> 29 <b>Header:</b> <a href="../headers/facilities/expand.html"><boost/preprocessor/facilities/expand.hpp></a> 30 </div> 31 <h4>Sample Code</h4> 32<div><pre> 33#include <<a href="../headers/control/if.html">boost/preprocessor/control/if.hpp</a>> 34#include <<a href="../headers/facilities/expand.html">boost/preprocessor/facilities/expand.hpp</a>> 35 36#define MACRO(a, b, c) (a)(b)(c) 37#define ARGS() (1, 2, 3) 38 39<a href="expand.html">BOOST_PP_EXPAND</a>(MACRO ARGS()) // expands to (1)(2)(3) 40 41#define SAMPLE(n) \ 42 <a href="expand.html">BOOST_PP_EXPAND</a>( \ 43 MACRO \ 44 <a href="if.html">BOOST_PP_IF</a>( \ 45 n, \ 46 (x, y, z), \ 47 (a, b, c) \ 48 ) \ 49 ) \ 50 /**/ 51 52SAMPLE(0) // expands to (a)(b)(c) 53SAMPLE(1) // expands to (x)(y)(z) 54</pre></div> 55 <hr size="1"> 56 <div style="margin-left: 0px;"> 57 <i>� Copyright <a href="http://www.housemarque.com" target="_top">Housemarque Oy</a> 2002</i> 58 </br><i>� Copyright Paul Mensonides 2002</i> 59 </div> 60 <div style="margin-left: 0px;"> 61 <p><small>Distributed under the Boost Software License, Version 1.0. (See 62 accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or 63 copy at <a href= 64 "http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a>)</small></p> 65 </div> 66</body> 67</html> 68