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52 lines
1.4 KiB
HTML
52 lines
1.4 KiB
HTML
<html>
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<head>
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<title>BOOST_PP_LIST_FIRST</title>
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<link rel="stylesheet" type="text/css" href="../styles.css">
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</head>
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<body>
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<div style="margin-left: 0px;">
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The <b>BOOST_PP_LIST_FIRST</b> macro expands to the head of a <i>list</i>.
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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_LIST_FIRST</b>(<i>list</i>)
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</div>
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<h4>Arguments</h4>
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<dl>
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<dt>list</dt>
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<dd>
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A non-nil <i>list</i>.
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</dd>
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</dl>
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<h4>Requirements</h4>
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<div>
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<b>Header:</b> <a href="../headers/list/adt.html"><boost/preprocessor/list/adt.hpp></a>
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</div>
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<h4>Sample Code</h4>
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<div><pre>
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#include <<a href="../headers/list/adt.html">boost/preprocessor/list/adt.hpp</a>>
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#define OLD \
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<a href="list_cons.html">BOOST_PP_LIST_CONS</a>( \
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a, \
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<a href="list_cons.html">BOOST_PP_LIST_CONS</a>( \
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b, \
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<a href="list_cons.html">BOOST_PP_LIST_CONS</a>( \
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c, \
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<a href="list_nil.html">BOOST_PP_LIST_NIL</a> \
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) \
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) \
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) \
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/**/
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#define NEW (a, (b, (c, <a href="nil.html">BOOST_PP_NIL</a>)))
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<a href="list_first.html">BOOST_PP_LIST_FIRST</a>(OLD) == <a href="list_first.html">BOOST_PP_LIST_FIRST</a>(NEW)
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// expands to a == a
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<a href="list_rest.html">BOOST_PP_LIST_REST</a>(OLD) == <a href="list_rest.html">BOOST_PP_LIST_REST</a>(NEW)
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// expands to (b, (c, <a href="nil.html">BOOST_PP_NIL</a>)) == (b, (c, <a href="nil.html">BOOST_PP_NIL</a>))
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</pre></div>
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</body>
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</html>
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