2006-08-22 15:57:13 +00:00
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<div class="titlepage"><div><div><h5 class="title">
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<a name="fusion.sequences.intrinsics.functions.at_key"></a><a href="at_key.html" title="at_key">at_key</a></h5></div></div></div>
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<a name="fusion.sequences.intrinsics.functions.at_key.description"></a><h6>
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2007-02-15 23:11:24 +00:00
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<a name="id1010731"></a>
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2006-08-22 15:57:13 +00:00
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<a href="at_key.html#fusion.sequences.intrinsics.functions.at_key.description">Description</a>
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</h6>
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<p>
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Returns the element associated with a Key from the sequence.
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</p>
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<a name="fusion.sequences.intrinsics.functions.at_key.synopsis"></a><h6>
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<a name="id1010760"></a>
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<a href="at_key.html#fusion.sequences.intrinsics.functions.at_key.synopsis">Synopsis</a>
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</h6>
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<pre class="programlisting">
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<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Key</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Sequence</span><span class="special">></span>
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<span class="keyword">typename</span> <a href="../metafunctions/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">Sequence</span><span class="special">,</span> <span class="identifier">Key</span><span class="special">>::</span><span class="identifier">type</span>
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<span class="identifier">at_key</span><span class="special">(</span><span class="identifier">Sequence</span><span class="special">&</span> <span class="identifier">seq</span><span class="special">);</span>
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<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Key</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Sequence</span><span class="special">></span>
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<span class="keyword">typename</span> <a href="../metafunctions/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">Sequence</span> <span class="keyword">const</span><span class="special">,</span> <span class="identifier">Key</span><span class="special">>::</span><span class="identifier">type</span>
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<span class="identifier">at_key</span><span class="special">(</span><span class="identifier">Sequence</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">seq</span><span class="special">);</span>
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</pre>
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<a name="fusion.sequences.intrinsics.functions.at_key.parameters"></a><h6>
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<a name="id1011053"></a>
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<a href="at_key.html#fusion.sequences.intrinsics.functions.at_key.parameters">Parameters</a>
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</h6>
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<div class="informaltable"><table class="table">
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<colgroup>
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<col>
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<col>
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</colgroup>
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<thead><tr>
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<th>Parameter</th>
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<th>Requirement</th>
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<th>Description</th>
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</tr></thead>
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<tbody>
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<tr>
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<td><code class="computeroutput"><span class="identifier">seq</span></code></td>
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<td>Model
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of <a href="../../concepts/associative_sequence.html" title="Associative
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Sequence">Associative
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Sequence</a>
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</td>
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<td>The sequence we wish to investigate.</td>
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</tr>
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<tr>
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<td><code class="computeroutput"><span class="identifier">Key</span></code></td>
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<td>Any
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type</td>
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<td>The queried key.</td>
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</tr>
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</tbody>
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2006-10-30 01:20:23 +00:00
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</table></div>
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2006-08-22 15:57:13 +00:00
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<a name="fusion.sequences.intrinsics.functions.at_key.expression_semantics"></a><h6>
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<a name="id1011151"></a>
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<a href="at_key.html#fusion.sequences.intrinsics.functions.at_key.expression_semantics">Expression
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Semantics</a>
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</h6>
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<pre class="programlisting">
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<span class="identifier">at_key</span><span class="special"><</span><span class="identifier">Key</span><span class="special">>(</span><span class="identifier">seq</span><span class="special">);</span>
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</pre>
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<p>
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<span class="bold"><strong>Return type</strong></span>: Returns a reference to
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the element associated with Key from the sequence <code class="computeroutput"><span class="identifier">seq</span></code>
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if <code class="computeroutput"><span class="identifier">seq</span></code> is mutable and
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<code class="computeroutput"><span class="identifier">e</span> <span class="special">=</span>
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<span class="identifier">o</span></code>, where <code class="computeroutput"><span class="identifier">e</span></code>
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is the element associated with Key, is a valid expression. Else, returns
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a type convertable to the element associated with Key.
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</p>
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<p>
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<span class="bold"><strong>Precondition</strong></span>: <code class="computeroutput"><span class="identifier">has_key</span><span class="special"><</span><span class="identifier">Key</span><span class="special">>(</span><span class="identifier">seq</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">true</span></code>
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</p>
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<p>
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<span class="bold"><strong>Semantics</strong></span>: Returns the element associated
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with Key.
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</p>
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<a name="fusion.sequences.intrinsics.functions.at_key.header"></a><h6>
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2007-02-15 23:11:24 +00:00
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<a name="id1011328"></a>
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2006-08-22 15:57:13 +00:00
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<a href="at_key.html#fusion.sequences.intrinsics.functions.at_key.header">Header</a>
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</h6>
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<pre class="programlisting">
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<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_key</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
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</pre>
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<a name="fusion.sequences.intrinsics.functions.at_key.example"></a><h6>
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2007-02-15 23:11:24 +00:00
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<a name="id1011421"></a>
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2006-08-22 15:57:13 +00:00
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<a href="at_key.html#fusion.sequences.intrinsics.functions.at_key.example">Example</a>
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</h6>
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<pre class="programlisting">
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<a href="../../containers/set.html" title="set"><code class="computeroutput"><span class="identifier">set</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> <span class="keyword">bool</span><span class="special">></span> <span class="identifier">s</span><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="char">'x'</span><span class="special">,</span> <span class="keyword">true</span><span class="special">);</span>
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<span class="identifier">assert</span><span class="special">(</span><span class="identifier">at_key</span><span class="special"><</span><span class="keyword">char</span><span class="special">>(</span><span class="identifier">s</span><span class="special">)</span> <span class="special">==</span> <span class="char">'x'</span><span class="special">);</span>
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</pre>
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<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
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<td align="left"></td>
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<td align="right"><small>Copyright <20> 2001-2005 Joel de Guzman, Dan Marsden</small></td>
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