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51 lines
1.5 KiB
HTML
51 lines
1.5 KiB
HTML
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<html>
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<head>
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<title>BOOST_PP_LIST_AT</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_AT</b> macro extracts an element in 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_AT</b>(<i>list</i>, <i>index</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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The <i>list</i> from which a element is to be extracted.
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This <i>list</i> must have at least <i>index</i> + <i>1</i> elements.
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</dd>
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<dt>index</dt>
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<dd>
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The zero-based position in the <i>list</i> of the element to be extracted.
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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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Previously, this macro could not be used inside <b>BOOST_PP_WHILE</b>.
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There is no longer any such restriction.
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It is more efficient, however, to use <b>BOOST_PP_LIST_AT_D</b> in such a situation.
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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="list_at_d.html">BOOST_PP_LIST_AT_D</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/list/at.hpp.html"><boost/preprocessor/list/at.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/at.hpp.html">boost/preprocessor/list/at.hpp</a>>
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#define LIST (a, (b, (c, <a href="nil.html">BOOST_PP_NIL</a>)))
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<a href="list_at.html">BOOST_PP_LIST_AT</a>(LIST, 0) // expands to a
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<a href="list_at.html">BOOST_PP_LIST_AT</a>(LIST, 2) // expands to c
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</pre></div>
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</body>
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</html>
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