boost_fusion/doc/html/fusion/sequences/intrinsics/functions/has_key.html

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<div class="titlepage"><div><div><h5 class="title">
<a name="fusion.sequences.intrinsics.functions.has_key"></a><a href="has_key.html" title="has_key">has_key</a></h5></div></div></div>
<a name="fusion.sequences.intrinsics.functions.has_key.description"></a><h6>
<a name="id509508"></a>
            <a href="has_key.html#fusion.sequences.intrinsics.functions.has_key.description">Description</a>
          </h6>
<p>
            Returns a type convertible to <tt class="computeroutput"><span class="keyword">bool</span></tt>
            that evaluates to <tt class="computeroutput"><span class="keyword">true</span></tt> if
            the sequence contains an element associated with a Key, else, evaluates
            to <tt class="computeroutput"><span class="keyword">false</span></tt>.
          </p>
<a name="fusion.sequences.intrinsics.functions.has_key.synopsis"></a><h6>
<a name="id509571"></a>
            <a href="has_key.html#fusion.sequences.intrinsics.functions.has_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">Key</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Sequence</span><span class="special">&gt;</span>
<span class="keyword">typename</span> <a href="../metafunctions/has_key.html" title="has_key"><tt class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">has_key</span></tt></a><span class="special">&lt;</span><span class="identifier">Sequence</span><span class="special">,</span> <span class="identifier">Key</span><span class="special">&gt;::</span><span class="identifier">type</span>
<span class="identifier">has_key</span><span class="special">(</span><span class="identifier">Sequence</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">seq</span><span class="special">);</span>
</pre>
<a name="fusion.sequences.intrinsics.functions.has_key.parameters"></a><h6>
<a name="id509754"></a>
            <a href="has_key.html#fusion.sequences.intrinsics.functions.has_key.parameters">Parameters</a>
          </h6>
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<h4>
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            </h4>
<table class="table">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>Parameter</th>
<th>Requirement</th>
<th>Description</th>
</tr></thead>
<tbody>
<tr>
<td><tt class="computeroutput"><span class="identifier">seq</span></tt></td>
<td>Model
                  of <a href="../../concepts/associative_sequence.html" title="Associative
        Sequence">Associative
                  Sequence</a>
</td>
<td>The sequence we wish to investigate.</td>
</tr>
<tr>
<td><tt class="computeroutput"><span class="identifier">Key</span></tt></td>
<td>Any
                  type</td>
<td>The queried key.</td>
</tr>
</tbody>
</table>
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<a name="fusion.sequences.intrinsics.functions.has_key.expression_semantics"></a><h6>
<a name="id509869"></a>
            <a href="has_key.html#fusion.sequences.intrinsics.functions.has_key.expression_semantics">Expression
            Semantics</a>
          </h6>
<pre class="programlisting">
<span class="identifier">has_key</span><span class="special">&lt;</span><span class="identifier">Key</span><span class="special">&gt;(</span><span class="identifier">seq</span><span class="special">);</span>
</pre>
<p>
            <span class="bold"><b>Return type</b></span>: Convertible to <tt class="computeroutput"><span class="keyword">bool</span></tt>.
          </p>
<p>
            <span class="bold"><b>Semantics</b></span>: Evaluates to <tt class="computeroutput"><span class="keyword">true</span></tt> if the sequence contains an element
            associated with Key, else, evaluates to <tt class="computeroutput"><span class="keyword">false</span></tt>.
          </p>
<a name="fusion.sequences.intrinsics.functions.has_key.header"></a><h6>
<a name="id509986"></a>
            <a href="has_key.html#fusion.sequences.intrinsics.functions.has_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">has_key</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
</pre>
<a name="fusion.sequences.intrinsics.functions.has_key.example"></a><h6>
<a name="id510092"></a>
            <a href="has_key.html#fusion.sequences.intrinsics.functions.has_key.example">Example</a>
          </h6>
<pre class="programlisting">
<a href="../../containers/set.html" title="set"><tt class="computeroutput"><span class="identifier">set</span></tt></a><span class="special">&lt;</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">&gt;</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>
<span class="identifier">assert</span><span class="special">(</span><span class="identifier">has_key</span><span class="special">&lt;</span><span class="keyword">char</span><span class="special">&gt;(</span><span class="identifier">s</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">true</span><span class="special">);</span>
</pre>
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