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52 lines
1.7 KiB
HTML
52 lines
1.7 KiB
HTML
<html>
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<head>
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<title>BOOST_PP_LPAREN_IF</title>
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<link rel="stylesheet" type="text/css" href="../styles.css">
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<script language="javascript" type="text/javascript" src="../scripts.js"></script>
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</head>
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<body onload="init('sample');">
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<div style="margin-left: 0px;">
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The <b>BOOST_PP_LPAREN_IF</b> macro conditionally expands to a left parenthesis.
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</div>
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<h4>Usage</h4>
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<div class="code">
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<b>BOOST_PP_LPAREN_IF</b>(<i>cond</i>)
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</div>
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<h4>Arguments</h4>
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<dl>
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<dt>cond</dt>
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<dd>
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The condition that determines if a the macro expands to a left parenthesis or nothing.
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Valid values range from <i>0</i> to <b>BOOST_PP_LIMIT_MAG</b>.
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</dd>
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</dl>
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<h4>Remarks</h4>
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<div>
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If <i>cond</i> expands to <i>0</i>, this macro expands to nothing.
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Otherwise, it expands to a left parenthesis.
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</div>
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<div>
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The preprocessor interprets parentheses as delimiters in macro invocations.
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Because of this, parentheses require special handling.
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</div>
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<h4>See Also</h4>
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<ul>
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<li><a href="limit_mag.html">BOOST_PP_LIMIT_MAG</a></li>
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<li><a href="rparen_if.html">BOOST_PP_RPAREN_IF</a></li>
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</ul>
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<h4>Requirements</h4>
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<div>
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<b>Header:</b> <a href="../headers/punctuation/paren_if.hpp.html"><boost/preprocessor/punctuation/paren_if.hpp></a>
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</div>
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<h4><a class="local" onclick="toggle('sample');" onmouseover="change(this);" onmouseout="revert(this);">Sample Code</a></h4>
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<div id="sample"><pre>
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#include <boost/preprocessor/punctuation/paren_if.hpp>
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#define MACRO(c, x) BOOST_PP_LPAREN_IF(c) x BOOST_PP_RPAREN_IF(c)
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MACRO(0, text) // expands to text
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MACRO(1, text) // expands to (text)
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<pre></div>
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</body>
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</html>
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