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| <title>The MPL Reference Manual: has_key</title> |
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| <td class="header-group page-location"><a href="../refmanual.html" class="navigation-link">Front Page</a> / <a href="./sequences.html" class="navigation-link">Sequences</a> / <a href="./intrinsic-metafunctions.html" class="navigation-link">Intrinsic Metafunctions</a> / <a href="./has-key.html" class="navigation-link">has_key</a></td> |
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| <div class="section" id="has-key"> |
| <h1><a class="toc-backref" href="./intrinsic-metafunctions.html#id1435">has_key</a></h1> |
| <div class="section" id="id265"> |
| <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> |
| <pre class="literal-block"> |
| template< |
| typename Sequence |
| , typename Key |
| > |
| struct <a href="./has-key.html" class="identifier">has_key</a> |
| { |
| typedef <em>unspecified</em> type; |
| }; |
| </pre> |
| </div> |
| <div class="section" id="id266"> |
| <h3><a class="subsection-title" href="#description" name="description">Description</a></h3> |
| <p>Returns a true-valued <a class="reference internal" href="./integral-constant.html">Integral Constant</a> if <tt class="literal"><span class="pre">Sequence</span></tt> contains an element |
| with key <tt class="literal"><span class="pre">Key</span></tt>.</p> |
| </div> |
| <div class="section" id="id267"> |
| <h3><a class="subsection-title" href="#header" name="header">Header</a></h3> |
| <pre class="literal-block"> |
| #include <<a href="../../../../boost/mpl/has_key.hpp" class="header">boost/mpl/has_key.hpp</a>> |
| </pre> |
| </div> |
| <div class="section" id="id268"> |
| <h3><a class="subsection-title" href="#model-of" name="model-of">Model of</a></h3> |
| <p><a class="reference internal" href="./tag-dispatched-metafunction.html">Tag Dispatched Metafunction</a></p> |
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| <div class="section" id="id269"> |
| <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> |
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| <tr><th class="head">Parameter</th> |
| <th class="head">Requirement</th> |
| <th class="head">Description</th> |
| </tr> |
| </thead> |
| <tbody valign="top"> |
| <tr><td><tt class="literal"><span class="pre">Sequence</span></tt></td> |
| <td><a class="reference internal" href="./associative-sequence.html">Associative Sequence</a></td> |
| <td>A sequence to query.</td> |
| </tr> |
| <tr><td><tt class="literal"><span class="pre">Key</span></tt></td> |
| <td>Any type</td> |
| <td>The queried key.</td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="section" id="id270"> |
| <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> |
| <p>For any <a class="reference internal" href="./associative-sequence.html">Associative Sequence</a> <tt class="literal"><span class="pre">s</span></tt>, and arbitrary type <tt class="literal"><span class="pre">key</span></tt>:</p> |
| <pre class="literal-block"> |
| typedef <a href="./has-key.html" class="identifier">has_key</a><s,key>::type c; |
| </pre> |
| <table class="docutils field-list" frame="void" rules="none"> |
| <col class="field-name" /> |
| <col class="field-body" /> |
| <tbody valign="top"> |
| <tr class="field"><th class="field-name">Return type:</th><td class="field-body">Boolean <a class="reference internal" href="./integral-constant.html">Integral Constant</a>.</td> |
| </tr> |
| <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><tt class="literal"><span class="pre">c::value</span> <span class="pre">==</span> <span class="pre">true</span></tt> if <tt class="literal"><span class="pre">key</span></tt> is in <tt class="literal"><span class="pre">s</span></tt>'s set of keys; otherwise |
| <tt class="literal"><span class="pre">c::value</span> <span class="pre">==</span> <span class="pre">false</span></tt>.</td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="section" id="id271"> |
| <h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3> |
| <p>Amortized constant time.</p> |
| </div> |
| <div class="section" id="id272"> |
| <h3><a class="subsection-title" href="#example" name="example">Example</a></h3> |
| <pre class="literal-block"> |
| typedef <a href="./map.html" class="identifier">map</a>< <a href="./pair.html" class="identifier">pair</a><int,unsigned>, <a href="./pair.html" class="identifier">pair</a><char,long> > m; |
| <a href="./assert-not.html" class="identifier">BOOST_MPL_ASSERT_NOT</a>(( <a href="./has-key.html" class="identifier">has_key</a><m,long> )); |
| |
| typedef <a href="./insert.html" class="identifier">insert</a>< m, <a href="./pair.html" class="identifier">pair</a><long,unsigned long> > m1; |
| <a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( <a href="./has-key.html" class="identifier">has_key</a><m1,long> )); |
| </pre> |
| </div> |
| <div class="section" id="id273"> |
| <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> |
| <p><a class="reference internal" href="./associative-sequence.html">Associative Sequence</a>, <a class="reference internal" href="./count.html">count</a>, <a class="reference internal" href="./insert.html">insert</a>, <a class="reference internal" href="./erase-key.html">erase_key</a></p> |
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