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<title>value_at_key</title>
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<div class="titlepage"><div><div><h5 class="title">
<a name="fusion.sequence.intrinsic.metafunctions.value_at_key"></a><a class="link" href="value_at_key.html" title="value_at_key">value_at_key</a>
</h5></div></div></div>
<h6>
<a name="fusion.sequence.intrinsic.metafunctions.value_at_key.h0"></a>
<span><a name="fusion.sequence.intrinsic.metafunctions.value_at_key.description"></a></span><a class="link" href="value_at_key.html#fusion.sequence.intrinsic.metafunctions.value_at_key.description">Description</a>
</h6>
<p>
Returns the actual element type associated with a Key from the <a class="link" href="../../../sequence.html" title="Sequence">Sequence</a>.
</p>
<h6>
<a name="fusion.sequence.intrinsic.metafunctions.value_at_key.h1"></a>
<span><a name="fusion.sequence.intrinsic.metafunctions.value_at_key.synopsis"></a></span><a class="link" href="value_at_key.html#fusion.sequence.intrinsic.metafunctions.value_at_key.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">Key</span><span class="special">></span>
<span class="keyword">struct</span> <span class="identifier">value_at_key</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.value_at_key.t0"></a><p class="title"><b>Table 1.35. 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/associative_sequence.html" title="Associative Sequence">Associative
Sequence</a>
</p>
</td>
<td>
<p>
Argument sequence
</p>
</td>
</tr>
<tr>
<td>
<p>
<code class="computeroutput"><span class="identifier">Key</span></code>
</p>
</td>
<td>
<p>
Any type
</p>
</td>
<td>
<p>
Key type
</p>
</td>
</tr>
</tbody>
</table></div>
</div>
<br class="table-break"><h6>
<a name="fusion.sequence.intrinsic.metafunctions.value_at_key.h2"></a>
<span><a name="fusion.sequence.intrinsic.metafunctions.value_at_key.expression_semantics"></a></span><a class="link" href="value_at_key.html#fusion.sequence.intrinsic.metafunctions.value_at_key.expression_semantics">Expression
Semantics</a>
</h6>
<pre class="programlisting"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_at_key</span><span class="special"><</span><span class="identifier">Seq</span><span class="special">,</span> <span class="identifier">Key</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 actual element
type associated with key type <code class="computeroutput"><span class="identifier">Key</span></code>
in <code class="computeroutput"><span class="identifier">Seq</span></code>.
</p>
<h6>
<a name="fusion.sequence.intrinsic.metafunctions.value_at_key.h3"></a>
<span><a name="fusion.sequence.intrinsic.metafunctions.value_at_key.header"></a></span><a class="link" href="value_at_key.html#fusion.sequence.intrinsic.metafunctions.value_at_key.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">value_at_key</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">value_at_key</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
</pre>
<h6>
<a name="fusion.sequence.intrinsic.metafunctions.value_at_key.h4"></a>
<span><a name="fusion.sequence.intrinsic.metafunctions.value_at_key.example"></a></span><a class="link" href="value_at_key.html#fusion.sequence.intrinsic.metafunctions.value_at_key.example">Example</a>
</h6>
<pre class="programlisting"><span class="keyword">typedef</span> <a class="link" href="../../../container/map.html" title="map"><code class="computeroutput"><span class="identifier">map</span></code></a><span class="special"><</span><a class="link" href="../../../support/pair.html" title="pair"><code class="computeroutput"><span class="identifier">pair</span></code></a><span class="special"><</span><span class="keyword">int</span><span class="special">,</span> <span class="keyword">char</span><span class="special">>,</span> <a class="link" href="../../../support/pair.html" title="pair"><code class="computeroutput"><span class="identifier">pair</span></code></a><span class="special"><</span><span class="keyword">char</span><span class="special">,</span> <span class="keyword">char</span><span class="special">>,</span> <a class="link" href="../../../support/pair.html" title="pair"><code class="computeroutput"><span class="identifier">pair</span></code></a><span class="special"><</span><span class="keyword">double</span><span class="special">,</span> <span class="keyword">char</span><span class="special">></span> <span class="special">></span> <span class="identifier">mymap</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_key.html" title="at_key"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">at_key</span></code></a><span class="special"><</span><span class="identifier">mymap</span><span class="special">,</span> <span class="keyword">int</span><span class="special">>::</span><span class="identifier">type</span><span class="special">,</span> <span class="keyword">char</span><span class="special">>));</span>
</pre>
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