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| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="fusion.sequence.intrinsic.functions.at"></a><a class="link" href="at.html" title="at">at</a> |
| </h5></div></div></div> |
| <a name="fusion.sequence.intrinsic.functions.at.description"></a><h6> |
| <a name="id883430"></a> |
| <a class="link" href="at.html#fusion.sequence.intrinsic.functions.at.description">Description</a> |
| </h6> |
| <p> |
| Returns the N-th element from the beginning of the sequence. |
| </p> |
| <a name="fusion.sequence.intrinsic.functions.at.synopsis"></a><h6> |
| <a name="id883447"></a> |
| <a class="link" href="at.html#fusion.sequence.intrinsic.functions.at.synopsis">Synopsis</a> |
| </h6> |
| <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">N</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Sequence</span><span class="special">></span> |
| <span class="keyword">typename</span> <a class="link" href="../metafunctions/at.html" title="at"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">at</span></code></a><span class="special"><</span><span class="identifier">Sequence</span><span class="special">,</span> <span class="identifier">N</span><span class="special">>::</span><span class="identifier">type</span> |
| <span class="identifier">at</span><span class="special">(</span><span class="identifier">Sequence</span><span class="special">&</span> <span class="identifier">seq</span><span class="special">);</span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">N</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Sequence</span><span class="special">></span> |
| <span class="keyword">typename</span> <a class="link" href="../metafunctions/at.html" title="at"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">at</span></code></a><span class="special"><</span><span class="identifier">Sequence</span> <span class="keyword">const</span><span class="special">,</span> <span class="identifier">N</span><span class="special">>::</span><span class="identifier">type</span> |
| <span class="identifier">at</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> |
| </pre> |
| <a name="fusion.sequence.intrinsic.functions.at.parameters"></a><h6> |
| <a name="id883679"></a> |
| <a class="link" href="at.html#fusion.sequence.intrinsic.functions.at.parameters">Parameters</a> |
| </h6> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Parameter |
| </p> |
| </th> |
| <th> |
| <p> |
| Requirement |
| </p> |
| </th> |
| <th> |
| <p> |
| Description |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">seq</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Model of <a class="link" href="../../concepts/random_access_sequence.html" title="Random Access Sequence">Random |
| Access Sequence</a> |
| </p> |
| </td> |
| <td> |
| <p> |
| The sequence we wish to investigate. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <code class="computeroutput"><span class="identifier">N</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| An <a href="http://www.boost.org/libs/mpl/doc/refmanual/integral-constant.html" target="_top">MPL |
| Integral Constant</a> |
| </p> |
| </td> |
| <td> |
| <p> |
| An index from the beginning of the sequence. |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| <a name="fusion.sequence.intrinsic.functions.at.expression_semantics"></a><h6> |
| <a name="id883811"></a> |
| <a class="link" href="at.html#fusion.sequence.intrinsic.functions.at.expression_semantics">Expression |
| Semantics</a> |
| </h6> |
| <pre class="programlisting"><span class="identifier">at</span><span class="special"><</span><span class="identifier">N</span><span class="special">>(</span><span class="identifier">seq</span><span class="special">);</span> |
| </pre> |
| <p> |
| <span class="bold"><strong>Return type</strong></span>: Returns a reference to |
| the N-th element from the beginning of the sequence <code class="computeroutput"><span class="identifier">seq</span></code> |
| if <code class="computeroutput"><span class="identifier">seq</span></code> is mutable and |
| <code class="computeroutput"><span class="identifier">e</span> <span class="special">=</span> |
| <span class="identifier">o</span></code>, where <code class="computeroutput"><span class="identifier">e</span></code> |
| is the N-th element from the beginning of the sequence, is a valid expression. |
| Else, returns a type convertable to the N-th element from the beginning |
| of the sequence. |
| </p> |
| <p> |
| <span class="bold"><strong>Precondition</strong></span>: <code class="computeroutput"><span class="number">0</span> |
| <span class="special"><=</span> <span class="identifier">N</span><span class="special">::</span><span class="identifier">value</span> <span class="special"><</span> <a class="link" href="size.html" title="size"><code class="computeroutput"><span class="identifier">size</span></code></a><span class="special">(</span><span class="identifier">s</span><span class="special">)</span></code> |
| </p> |
| <p> |
| <span class="bold"><strong>Semantics</strong></span>: Equivalent to |
| </p> |
| <pre class="programlisting"><a class="link" href="../../../iterator/functions/deref.html" title="deref"><code class="computeroutput"><span class="identifier">deref</span></code></a><span class="special">(</span><a class="link" href="../../../iterator/functions/advance.html" title="advance"><code class="computeroutput"><span class="identifier">advance</span></code></a><span class="special"><</span><span class="identifier">N</span><span class="special">>(</span><a class="link" href="begin.html" title="begin"><code class="computeroutput"><span class="identifier">begin</span></code></a><span class="special">(</span><span class="identifier">s</span><span class="special">)))</span> |
| </pre> |
| <a name="fusion.sequence.intrinsic.functions.at.header"></a><h6> |
| <a name="id884021"></a> |
| <a class="link" href="at.html#fusion.sequence.intrinsic.functions.at.header">Header</a> |
| </h6> |
| <pre class="programlisting"><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</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <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">include</span><span class="special">/</span><span class="identifier">at</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| </pre> |
| <a name="fusion.sequence.intrinsic.functions.at.example"></a><h6> |
| <a name="id884137"></a> |
| <a class="link" href="at.html#fusion.sequence.intrinsic.functions.at.example">Example</a> |
| </h6> |
| <pre class="programlisting"><a class="link" href="../../../container/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a><span class="special"><</span><span class="keyword">int</span><span class="special">,</span> <span class="keyword">int</span><span class="special">,</span> <span class="keyword">int</span><span class="special">></span> <span class="identifier">v</span><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="number">2</span><span class="special">,</span> <span class="number">3</span><span class="special">);</span> |
| <span class="identifier">assert</span><span class="special">(</span><span class="identifier">at</span><span class="special"><</span><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">int_</span><span class="special"><</span><span class="number">1</span><span class="special">></span> <span class="special">>(</span><span class="identifier">v</span><span class="special">)</span> <span class="special">==</span> <span class="number">2</span><span class="special">);</span> |
| </pre> |
| </div> |
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| <td align="right"><div class="copyright-footer">Copyright © 2001-2007 Joel de Guzman, Dan Marsden, Tobias |
| Schwinger<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) |
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