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<html>
<head>
<title>BOOST_PP_EXPAND</title>
<link rel="stylesheet" type="text/css" href="../styles.css">
</head>
<body>
<div style="margin-left: 0px;">
The <b>BOOST_PP_EXPAND</b> macro performs a double macro-expansion on its argument.
</div>
<h4>Usage</h4>
<div class="code">
<b>BOOST_PP_EXPAND</b>(<i>x</i>)
</div>
<h4>Arguments</h4>
<dl>
<dt>x</dt>
<dd>
The argument to be expanded twice.
</dd>
</dl>
<h4>Remarks</h4>
<div>
This macro is useful when a delay is necessary to produce the correct semantics of a macro invocation.
For example, when a macro expands to an argument list to another macro.
This macro will expand the the argument list on the first pass, and then rescan to expand any more macros.
</div>
<h4>Requirements</h4>
<div>
<b>Header:</b> <a href="../headers/facilities/expand.html"><boost/preprocessor/facilities/expand.hpp></a>
</div>
<h4>Sample Code</h4>
<div><pre>
#include <<a href="../headers/control/if.html">boost/preprocessor/control/if.hpp</a>>
#include <<a href="../headers/facilities/expand.html">boost/preprocessor/facilities/expand.hpp</a>>
#define MACRO(a, b, c) (a)(b)(c)
#define ARGS() (1, 2, 3)
<a href="expand.html">BOOST_PP_EXPAND</a>(MACRO ARGS()) // expands to (1)(2)(3)
#define SAMPLE(n) \
<a href="expand.html">BOOST_PP_EXPAND</a>( \
MACRO \
<a href="if.html">BOOST_PP_IF</a>( \
n, \
(x, y, z), \
(a, b, c) \
) \
) \
/**/
SAMPLE(0) // expands to (a)(b)(c)
SAMPLE(1) // expands to (x)(y)(z)
</pre></div>
<hr size="1">
<div style="margin-left: 0px;">
<i>© Copyright <a href="http://www.housemarque.com" target="_top">Housemarque Oy</a> 2002</i>
</br><i>© Copyright Paul Mensonides 2002</i>
</div>
<div style="margin-left: 0px;">
<p><small>Distributed under the Boost Software License, Version 1.0. (See
accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> or
copy at <a href=
"http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a>)</small></p>
</div>
</body>
</html>
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