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boost_fusion/doc/html/fusion/sequences/intrinsics/metafunctions/at_key.html
Tobias Schwinger ca6f831b96 adds documentation for functional module 
[SVN r36959]
2007-02-15 23:11:24 +00:00

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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>at_key</title>
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<div class="section" lang="en">
<div class="titlepage"><div><div><h5 class="title">
<a name="fusion.sequences.intrinsics.metafunctions.at_key"></a><a href="at_key.html" title="at_key">at_key</a></h5></div></div></div>
<a name="fusion.sequences.intrinsics.metafunctions.at_key.description"></a><h6>
<a name="id1036491"></a>
<a href="at_key.html#fusion.sequences.intrinsics.metafunctions.at_key.description">Description</a>
</h6>
<p>
Returns the result type of <a href="../functions/at_key.html" title="at_key"><code class="computeroutput"><span class="identifier">at_key</span></code></a>
<sup>[<a name="id1036524" href="#ftn.id1036524">8</a>]</sup>
.
</p>
<a name="fusion.sequences.intrinsics.metafunctions.at_key.synopsis"></a><h6>
<a name="id1036625"></a>
<a href="at_key.html#fusion.sequences.intrinsics.metafunctions.at_key.synopsis">Synopsis</a>
</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">Key</span><span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">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="id1036728"></a><p class="title"><b>Table 1.30. Parameters</b></p>
<table class="table" summary="Parameters">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>Parameter</th>
<th>Requirement</th>
<th>Description</th>
</tr></thead>
<tbody>
<tr>
<td><code class="computeroutput"><span class="identifier">Seq</span></code></td>
<td>A
model of <a href="../../concepts/forward_sequence.html" title="Forward
Sequence">Forward
Sequence</a>
</td>
<td>Argument sequence</td>
</tr>
<tr>
<td><code class="computeroutput"><span class="identifier">Key</span></code></td>
<td>Any
type</td>
<td>Key type</td>
</tr>
</tbody>
</table>
</div>
<a name="fusion.sequences.intrinsics.metafunctions.at_key.expression_semantics"></a><h6>
<a name="id1036813"></a>
<a href="at_key.html#fusion.sequences.intrinsics.metafunctions.at_key.expression_semantics">Expression
Semantics</a>
</h6>
<pre class="programlisting">
<span class="identifier">result_of</span><span class="special">::</span><span class="identifier">at_key</span><span class="special">&lt;</span><span class="identifier">Seq</span><span class="special">,</span> <span class="identifier">Key</span><span class="special">&gt;::</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 of using
<a href="../functions/at_key.html" title="at_key"><code class="computeroutput"><span class="identifier">at_key</span></code></a> to access the element
with key type <code class="computeroutput"><span class="identifier">Key</span></code> in
<code class="computeroutput"><span class="identifier">Seq</span></code>.
</p>
<a name="fusion.sequences.intrinsics.metafunctions.at_key.header"></a><h6>
<a name="id1036936"></a>
<a href="at_key.html#fusion.sequences.intrinsics.metafunctions.at_key.header">Header</a>
</h6>
<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_key</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
</pre>
<a name="fusion.sequences.intrinsics.metafunctions.at_key.example"></a><h6>
<a name="id1037029"></a>
<a href="at_key.html#fusion.sequences.intrinsics.metafunctions.at_key.example">Example</a>
</h6>
<pre class="programlisting">
<span class="keyword">typedef</span> <a href="../../containers/map.html" title="map"><code class="computeroutput"><span class="identifier">map</span></code></a><span class="special">&lt;</span><a href="../../../support/pair.html" title="pair"><code class="computeroutput"><span class="identifier">pair</span></code></a><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span> <span class="keyword">char</span><span class="special">&gt;,</span> <a href="../../../support/pair.html" title="pair"><code class="computeroutput"><span class="identifier">pair</span></code></a><span class="special">&lt;</span><span class="keyword">char</span><span class="special">,</span> <span class="keyword">char</span><span class="special">&gt;,</span> <a href="../../../support/pair.html" title="pair"><code class="computeroutput"><span class="identifier">pair</span></code></a><span class="special">&lt;</span><span class="keyword">double</span><span class="special">,</span> <span class="keyword">char</span><span class="special">&gt;</span> <span class="special">&gt;</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">&lt;</span><a 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">&lt;</span><span class="identifier">mymap</span><span class="special">,</span> <span class="keyword">int</span><span class="special">&gt;::</span><span class="identifier">type</span><span class="special">,</span> <span class="keyword">char</span><span class="special">&amp;&gt;));</span>
</pre>
<div class="footnotes">
<br><hr width="100" align="left">
<div class="footnote"><p><sup>[<a name="ftn.id1036524" href="#id1036524">8</a>] </sup>
<a 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> reflects the actual
return type of the function <a href="../functions/at_key.html" title="at_key"><code class="computeroutput"><span class="identifier">at_key</span></code></a>. <span class="underline">_sequence</span>_s
typically return references to its elements via the <a href="../functions/at_key.html" title="at_key"><code class="computeroutput"><span class="identifier">at_key</span></code></a> function. If you
want to get the actual element type, use <a href="value_at_key.html" title="value_at_key"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_at_key</span></code></a>
</p></div>
</div>
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