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<title>BOOST_PP_LIST_AT_D</title>
<link rel="stylesheet" type="text/css" href="../styles.css">
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<div style="margin-left: 0px;">
The <b>BOOST_PP_LIST_AT_D</b> macro extracts an element in a <i>list</i>.
It reenters <b>BOOST_PP_WHILE</b> with maximum efficiency.
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<h4>Usage</h4>
<div class="code">
<b>BOOST_PP_LIST_AT_D</b>(<i>d</i>, <i>list</i>, <i>index</i>)
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<h4>Arguments</h4>
<dl>
<dt>d</dt>
<dd>
The next available <b>BOOST_PP_WHILE</b> iteration.
</dd>
<dt>list</dt>
<dd>
The <i>list</i> from which a element is to be extracted.
This <i>list</i> must have at least <i>index</i> + <i>1</i> elements.
</dd>
<dt>index</dt>
<dd>
The zero-based position in the <i>list</i> of the element to be extracted.
</dd>
</dl>
<h4>See Also</h4>
<ul>
<li><a href="list_at.html">BOOST_PP_LIST_AT</a></li>
</ul>
<h4>Requirements</h4>
<div>
<b>Header:</b> <a href="../headers/list/at.html"><boost/preprocessor/list/at.hpp></a>
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<h4>Sample Code</h4>
<div><pre>
#include <<a href="../headers/control/while.html">boost/preprocessor/control/while.hpp</a>>
#include <<a href="../headers/list/at.html">boost/preprocessor/list/at.hpp</a>>
#define LIST (7, (2, (0, (1, <a href="nil.html">BOOST_PP_NIL</a>))))
#define PRED(d, state) <a href="list_at_d.html">BOOST_PP_LIST_AT_D</a>(d, state, 0)
#define OP(d, state) <a href="list_rest.html">BOOST_PP_LIST_REST</a>(state)
<a href="while.html">BOOST_PP_WHILE</a>(PRED, OP, LIST) // expands to (0, (1, <a href="nil.html">BOOST_PP_NIL</a>))
</pre></div>
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