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[SVN r15693]
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Paul Mensonides
2002-10-03 22:13:37 +00:00
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<html>
<head>
<title>BOOST_PP_COMMA_IF</title>
<link rel="stylesheet" type="text/css" href="../styles.css">
</head>
<body>
<div style="margin-left: 0px;">
The <b>BOOST_PP_COMMA_IF</b> macro conditionally expands to a comma.
</div>
<h4>Usage</h4>
<div class="code">
<b>BOOST_PP_COMMA_IF</b>(<i>cond</i>)
</div>
<h4>Arguments</h4>
<dl>
<dt>cond</dt>
<dd>
The condition that determines if a the macro expands to a comma or nothing.&nbsp;
Valid values range from <i>0</i> to <b>BOOST_PP_LIMIT_MAG</b>.
</dd>
</dl>
<h4>Remarks</h4>
<div>
If <i>cond</i> expands to <i>0</i>, this macro expands to nothing.&nbsp;
Otherwise, it expands to a comma.
</div>
<div>
The preprocessor interprets commas as argument separators in macro invocations.&nbsp;
Because of this, commas require special handling.
</div>
<h4>See Also</h4>
<ul>
<li><a href="limit_mag.html">BOOST_PP_LIMIT_MAG</a></li>
</ul>
<h4>Requirements</h4>
<div>
<b>Header:</b> &nbsp;<a href="../headers/punctuation/comma_if.hpp.html">&lt;boost/preprocessor/punctuation/comma_if.hpp&gt;</a>
</div>
<h4>Sample Code</h4>
<div><pre>
#include &lt;<a href="../headers/punctuation/comma_if.hpp.html">boost/preprocessor/punctuation/comma_if.hpp</a>&gt;
#include &lt;<a href="../headers/repetition/repeat.hpp.html">boost/preprocessor/repetition/repeat.hpp</a>&gt;
#define MACRO(z, n, text) <a href="comma_if.html">BOOST_PP_COMMA_IF</a>(n) text
<a href="repeat.html">BOOST_PP_REPEAT</a>(3, MACRO, class) // expands to class, class, class
</pre></div>
</body>
</html>