mirror of
https://github.com/boostorg/preprocessor.git
synced 2025-07-15 21:42:08 +02:00
52 lines
1.6 KiB
HTML
52 lines
1.6 KiB
HTML
|
<html>
|
||
|
|
<head>
|
||
|
|
<title>BOOST_PP_LIST_AT</title>
|
||
|
|
<link rel="stylesheet" type="text/css" href="../styles.css">
|
||
|
|
<script language="javascript" type="text/javascript" src="../scripts.js"></script>
|
||
|
|
</head>
|
||
|
|
<body onload="init('sample');">
|
||
|
|
<div style="margin-left: 0px;">
|
||
|
|
The <b>BOOST_PP_LIST_AT</b> macro extracts an element in a <i>list</i>.
|
||
|
|
</div>
|
||
|
|
<h4>Usage</h4>
|
||
|
|
<div class="code">
|
||
|
|
<b>BOOST_PP_LIST_AT</b>(<i>list</i>, <i>index</i>)
|
||
|
|
</div>
|
||
|
|
<h4>Arguments</h4>
|
||
|
|
<dl>
|
||
|
|
<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>Remarks</h4>
|
||
|
|
<div>
|
||
|
|
Previously, this macro could not be used inside <b>BOOST_PP_WHILE</b>.
|
||
|
|
There is no longer any such restriction.
|
||
|
|
It is more efficient, however, to use <b>BOOST_PP_LIST_AT_D</b> in such a situation.
|
||
|
|
</div>
|
||
|
|
<h4>See Also</h4>
|
||
|
|
<ul>
|
||
|
|
<li><a href="list_at_d.html">BOOST_PP_LIST_AT_D</a></li>
|
||
|
|
</ul>
|
||
|
|
<h4>Requirements</h4>
|
||
|
|
<div>
|
||
|
|
<b>Header:</b> <a href="../headers/list/at.hpp.html"><boost/preprocessor/list/at.hpp></a>
|
||
|
|
</div>
|
||
|
|
<h4><a class="local" onclick="toggle('sample');" onmouseover="change(this);" onmouseout="revert(this);">Sample Code</a></h4>
|
||
|
|
<div id="sample"><pre>
|
||
|
|
#include <boost/preprocessor/list/at.hpp>
|
||
|
|
|
||
|
|
#define LIST (a, (b, (c, BOOST_PP_NIL)))
|
||
|
|
|
||
|
|
BOOST_PP_LIST_AT(LIST, 0) // expands to a
|
||
|
|
BOOST_PP_LIST_AT(LIST, 2) // expands to c
|
||
|
|
<pre></div>
|
||
|
|
</body>
|
||
|
|
</html>
|