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<div class="section">
<div class="titlepage"><div><div><h5 class="title">
<a name="fusion.sequence.intrinsic.metafunctions.at"></a><a class="link" href="at.html" title="at">at</a>
</h5></div></div></div>
<h6>
<a name="fusion.sequence.intrinsic.metafunctions.at.h0"></a>
<span><a name="fusion.sequence.intrinsic.metafunctions.at.description"></a></span><a class="link" href="at.html#fusion.sequence.intrinsic.metafunctions.at.description">Description</a>
</h6>
<p>
Returns the result type of <a class="link" href="../functions/at.html" title="at"><code class="computeroutput"><span class="identifier">at</span></code></a><sup>[<a name="fusion.sequence.intrinsic.metafunctions.at.f0" href="#ftn.fusion.sequence.intrinsic.metafunctions.at.f0" class="footnote">6</a>]</sup>.
</p>
<h6>
<a name="fusion.sequence.intrinsic.metafunctions.at.h1"></a>
<span><a name="fusion.sequence.intrinsic.metafunctions.at.synopsis"></a></span><a class="link" href="at.html#fusion.sequence.intrinsic.metafunctions.at.synopsis">Synopsis</a>
</h6>
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span>
<span class="keyword">typename</span> <span class="identifier">Seq</span><span class="special">,</span>
<span class="keyword">typename</span> <span class="identifier">N</span><span class="special">></span>
<span class="keyword">struct</span> <span class="identifier">at</span>
<span class="special">{</span>
<span class="keyword">typedef</span> <span class="emphasis"><em>unspecified</em></span> <span class="identifier">type</span><span class="special">;</span>
<span class="special">};</span>
</pre>
<div class="table">
<a name="fusion.sequence.intrinsic.metafunctions.at.t0"></a><p class="title"><b>Table 1.29. Parameters</b></p>
<div class="table-contents"><table class="table" summary="Parameters">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Parameter
</p>
</th>
<th>
<p>
Requirement
</p>
</th>
<th>
<p>
Description
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">Seq</span></code>
</p>
</td>
<td>
<p>
A model of <a class="link" href="../../concepts/random_access_sequence.html" title="Random Access Sequence">Random
Access Sequence</a>
</p>
</td>
<td>
<p>
Argument sequence
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">N</span></code>
</p>
</td>
<td>
<p>
An <a href="http://www.boost.org/libs/mpl/doc/refmanual/integral-constant.html" target="_top">MPL
Integral Constant</a>
</p>
</td>
<td>
<p>
Index of element
</p>
</td>
</tr>
</tbody>
</table></div>
</div>
<br class="table-break"><h6>
<a name="fusion.sequence.intrinsic.metafunctions.at.h2"></a>
<span><a name="fusion.sequence.intrinsic.metafunctions.at.expression_semantics"></a></span><a class="link" href="at.html#fusion.sequence.intrinsic.metafunctions.at.expression_semantics">Expression
Semantics</a>
</h6>
<pre class="programlisting"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">at</span><span class="special"><</span><span class="identifier">Seq</span><span class="special">,</span> <span class="identifier">N</span><span class="special">>::</span><span class="identifier">type</span>
</pre>
<p>
<span class="bold"><strong>Return type</strong></span>: Any type.
</p>
<p>
<span class="bold"><strong>Semantics</strong></span>: Returns the result type of
using <a class="link" href="../functions/at.html" title="at"><code class="computeroutput"><span class="identifier">at</span></code></a> to access the <code class="computeroutput"><span class="identifier">N</span></code>th element of <code class="computeroutput"><span class="identifier">Seq</span></code>.
</p>
<h6>
<a name="fusion.sequence.intrinsic.metafunctions.at.h3"></a>
<span><a name="fusion.sequence.intrinsic.metafunctions.at.header"></a></span><a class="link" href="at.html#fusion.sequence.intrinsic.metafunctions.at.header">Header</a>
</h6>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">sequence</span><span class="special">/</span><span class="identifier">intrinsic</span><span class="special">/</span><span class="identifier">at</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">at</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
</pre>
<h6>
<a name="fusion.sequence.intrinsic.metafunctions.at.h4"></a>
<span><a name="fusion.sequence.intrinsic.metafunctions.at.example"></a></span><a class="link" href="at.html#fusion.sequence.intrinsic.metafunctions.at.example">Example</a>
</h6>
<pre class="programlisting"><span class="keyword">typedef</span> <a class="link" href="../../../container/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a><span class="special"><</span><span class="keyword">int</span><span class="special">,</span><span class="keyword">float</span><span class="special">,</span><span class="keyword">char</span><span class="special">></span> <span class="identifier">vec</span><span class="special">;</span>
<span class="identifier">BOOST_MPL_ASSERT</span><span class="special">((</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_same</span><span class="special"><</span><a class="link" href="at.html" title="at"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">at</span></code></a><span class="special"><</span><span class="identifier">vec</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">int_</span><span class="special"><</span><span class="number">1</span><span class="special">></span> <span class="special">>::</span><span class="identifier">type</span><span class="special">,</span> <span class="keyword">float</span><span class="special">&>));</span>
</pre>
<div class="footnotes">
<br><hr width="100" align="left">
<div class="footnote"><p><sup>[<a id="ftn.fusion.sequence.intrinsic.metafunctions.at.f0" href="#fusion.sequence.intrinsic.metafunctions.at.f0" class="para">6</a>] </sup>
<a class="link" href="at.html" title="at"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">at</span></code></a> reflects the actual return
type of the function <a class="link" href="../functions/at.html" title="at"><code class="computeroutput"><span class="identifier">at</span></code></a>. <a class="link" href="../../../sequence.html" title="Sequence">Sequence</a>(s)
typically return references to its elements via the <a class="link" href="../functions/at.html" title="at"><code class="computeroutput"><span class="identifier">at</span></code></a> function. If you want to
get the actual element type, use <a class="link" href="value_at.html" title="value_at"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_at</span></code></a>
</p></div>
</div>
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<td align="right"><div class="copyright-footer">Copyright © 2001-2006, 2011, 2012 Joel de Guzman,
Dan Marsden, Tobias Schwinger<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
</p>
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