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| <title>The MPL Reference Manual: at_c</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="./at-c.html" class="navigation-link">at_c</a></td> |
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| <div class="section" id="at-c"> |
| <h1><a class="toc-backref" href="./intrinsic-metafunctions.html#id1426">at_c</a></h1> |
| <div class="section" id="id185"> |
| <h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3> |
| <pre class="literal-block"> |
| template< |
| typename Sequence |
| , long n |
| > |
| struct <a href="./at-c.html" class="identifier">at_c</a> |
| { |
| typedef <em>unspecified</em> type; |
| }; |
| </pre> |
| </div> |
| <div class="section" id="id186"> |
| <h3><a class="subsection-title" href="#description" name="description">Description</a></h3> |
| <p>Returns a type identical to the <tt class="literal"><span class="pre">n</span></tt>th element from the beginning of |
| the sequence. <tt class="literal"><span class="pre"><a href="./at-c.html" class="identifier">at_c</a><Sequence,n>::type</span></tt> is a shorcut notation for |
| <tt class="literal"><span class="pre"><a href="./at.html" class="identifier">at</a><</span> <span class="pre">Sequence,</span> <span class="pre"><a href="./long.html" class="identifier">long_</a><n></span> <span class="pre">>::type</span></tt>.</p> |
| </div> |
| <div class="section" id="id187"> |
| <h3><a class="subsection-title" href="#header" name="header">Header</a></h3> |
| <pre class="literal-block"> |
| #include <<a href="../../../../boost/mpl/at.hpp" class="header">boost/mpl/at.hpp</a>> |
| </pre> |
| </div> |
| <div class="section" id="id188"> |
| <h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3> |
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| <col width="15%" /> |
| <col width="36%" /> |
| <col width="48%" /> |
| </colgroup> |
| <thead valign="bottom"> |
| <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="./forward-sequence.html">Forward Sequence</a></td> |
| <td>A sequence to be examined.</td> |
| </tr> |
| <tr><td><tt class="literal"><span class="pre">n</span></tt></td> |
| <td>A compile-time integral constant</td> |
| <td>An offset from the beginning of the sequence |
| specifying the element to be retrieved.</td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="section" id="id189"> |
| <h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3> |
| <pre class="literal-block"> |
| typedef <a href="./at-c.html" class="identifier">at_c</a><Sequence,n>::type t; |
| </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"><p class="first">A type</p> |
| </td> |
| </tr> |
| <tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><p class="first"><tt class="literal"><span class="pre">0</span> <span class="pre"><=</span> <span class="pre">n</span> <span class="pre"><</span> <span class="pre"><a href="./size.html" class="identifier">size</a><Sequence>::value</span></tt></p> |
| </td> |
| </tr> |
| <tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to</p> |
| <pre class="last literal-block"> |
| typedef <a href="./at.html" class="identifier">at</a>< Sequence, <a href="./long.html" class="identifier">long_</a><n> >::type t; |
| </pre> |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="section" id="id190"> |
| <h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3> |
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| <col width="53%" /> |
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| <thead valign="bottom"> |
| <tr><th class="head">Sequence archetype</th> |
| <th class="head">Complexity</th> |
| </tr> |
| </thead> |
| <tbody valign="top"> |
| <tr><td><a class="reference internal" href="./forward-sequence.html">Forward Sequence</a></td> |
| <td>Linear.</td> |
| </tr> |
| <tr><td><a class="reference internal" href="./random-access-sequence.html">Random Access Sequence</a></td> |
| <td>Amortized constant time.</td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| <div class="section" id="id191"> |
| <h3><a class="subsection-title" href="#example" name="example">Example</a></h3> |
| <pre class="literal-block"> |
| typedef <a href="./range-c.html" class="identifier">range_c</a><long,10,50> range; |
| <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( (<a href="./at-c.html" class="identifier">at_c</a>< range,0 >::type::value), ==, 10 ); |
| <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( (<a href="./at-c.html" class="identifier">at_c</a>< range,10 >::type::value), ==, 20 ); |
| <a href="./assert-relation.html" class="identifier">BOOST_MPL_ASSERT_RELATION</a>( (<a href="./at-c.html" class="identifier">at_c</a>< range,40 >::type::value), ==, 50 ); |
| </pre> |
| </div> |
| <div class="section" id="id192"> |
| <h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3> |
| <p><a class="reference internal" href="./forward-sequence.html">Forward Sequence</a>, <a class="reference internal" href="./random-access-sequence.html">Random Access Sequence</a>, <a class="reference internal" href="./at.html">at</a>, <a class="reference internal" href="./front.html">front</a>, <a class="reference internal" href="./back.html">back</a></p> |
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