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<div><div><h5 class="title">
<a name="fusion.sequence.intrinsic.metafunctions.at"></a><a href="at.html" title="at">at</a>
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<a name="fusion.sequence.intrinsic.metafunctions.at.description"></a><h6>
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<a href="at.html#fusion.sequence.intrinsic.metafunctions.at.description">Description</a>
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<p>
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Returns the result type of <a href="../functions/at.html" title="at"><tt class="computeroutput"><span class="identifier">at</span></tt></a>
<sup>[<a name="id463929" href="#ftn.id463929">6</a>]</sup>
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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="id676747" href="#ftn.id676747" class="footnote">6</a>]</sup>
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.
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<a name="fusion.sequence.intrinsic.metafunctions.at.synopsis"></a><h6>
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<a class="link" href="at.html#fusion.sequence.intrinsic.metafunctions.at.synopsis">Synopsis</a>
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</h6>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</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">&gt;</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>
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<a name="id464162"></a><p class="title"><b>Table 1.25. Parameters</b></p>
<table class="table" summary="Parameters">
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<a name="id677756"></a><p class="title"><b>Table 1.29. Parameters</b></p>
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<a name="id691516"></a><p class="title"><b>Table&#160;1.29.&#160;Parameters</b></p>
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<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>
<tt class="computeroutput"><span class="identifier">Seq</span></tt>
</p></td>
<td><p>
A model of <a href="../../concepts/forward_sequence.html" title="Forward
Sequence">Forward
Sequence</a>
</p></td>
<td><p>
Argument sequence
</p></td>
</tr>
<tr>
<td><p>
<tt class="computeroutput"><span class="identifier">N</span></tt>
</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>
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<a name="fusion.sequence.intrinsic.metafunctions.at.expression_semantics"></a><h6>
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<a href="at.html#fusion.sequence.intrinsic.metafunctions.at.expression_semantics">Expression
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Semantics</a>
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<pre class="programlisting"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">at</span><span class="special">&lt;</span><span class="identifier">Seq</span><span class="special">,</span> <span class="identifier">N</span><span class="special">&gt;::</span><span class="identifier">type</span>
</pre>
<p>
<span class="bold"><b>Return type</b></span>: Any type.
</p>
<p>
<span class="bold"><b>Semantics</b></span>: Returns the result type of
using <a href="../functions/at.html" title="at"><tt class="computeroutput"><span class="identifier">at</span></tt></a> to access the <tt class="computeroutput"><span class="identifier">N</span></tt>th element of <tt class="computeroutput"><span class="identifier">Seq</span></tt>.
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<a class="link" href="at.html#fusion.sequence.intrinsic.metafunctions.at.header">Header</a>
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<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</span>
</pre>
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<pre class="programlisting"><span class="keyword">typedef</span> <a href="../../../container/vector.html" title="vector"><tt class="computeroutput"><span class="identifier">vector</span></tt></a><span class="special">&lt;</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">&gt;</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">&lt;</span><a href="at.html" title="at"><tt class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">at</span></tt></a><span class="special">&lt;</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">&lt;</span><span class="number">1</span><span class="special">&gt;</span> <span class="special">&gt;::</span><span class="identifier">type</span><span class="special">,</span> <span class="keyword">float</span><span class="special">&amp;&gt;));</span>
</pre>
<div class="footnotes">
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<div class="footnote"><p><sup>[<a name="ftn.id463929" href="#id463929">6</a>] </sup>
<a href="at.html" title="at"><tt class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">at</span></tt></a> reflects the actual return
type of the function <a href="../functions/at.html" title="at"><tt class="computeroutput"><span class="identifier">at</span></tt></a>. <a href="../../../sequence.html" title="Sequence">Sequence</a>(s)
typically return references to its elements via the <a href="../functions/at.html" title="at"><tt class="computeroutput"><span class="identifier">at</span></tt></a> function. If you want
to get the actual element type, use <a href="value_at.html" title="value_at"><tt class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_at</span></tt></a>
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<div class="footnote"><p><sup>[<a name="ftn.id669956" href="#id669956" class="para">6</a>] </sup>
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<div class="footnote"><p><sup>[<a name="ftn.id691362" href="#id691362" class="para">6</a>] </sup>
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<div class="footnote"><p><sup>[<a name="ftn.id680024" href="#id680024" class="para">6</a>] </sup>
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<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>
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</p></div>
</div>
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright &#169; 2001-2007 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>)
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