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9df373af5f53cd6ca0e349d03ff306fbfc156714
boost_fusion/doc/html/fusion/iterators/metafunctions/value_of.html
Tobias Schwinger 9df373af5f revises function object concepts and functional module documenation to reflect 
boost::result_of-based result computation


[SVN r38209]
2007-07-13 19:25:34 +00:00

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<a accesskey="p" href="../metafunctions.html"><img src="../../../images/prev.png" alt="Prev"></a><a accesskey="u" href="../metafunctions.html"><img src="../../../images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../images/home.png" alt="Home"></a><a accesskey="n" href="deref.html"><img src="../../../images/next.png" alt="Next"></a>
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<div class="titlepage"><div><div><h4 class="title">
<a name="fusion.iterators.metafunctions.value_of"></a><a href="value_of.html" title="value_of">value_of</a></h4></div></div></div>
<a name="fusion.iterators.metafunctions.value_of.description"></a><h5>
<a name="id962804"></a>
<a href="value_of.html#fusion.iterators.metafunctions.value_of.description">Description</a>
</h5>
<p>
Returns the type stored at the position of an iterator.
</p>
<a name="fusion.iterators.metafunctions.value_of.synopsis"></a><h5>
<a name="id962832"></a>
<a href="value_of.html#fusion.iterators.metafunctions.value_of.synopsis">Synopsis</a>
</h5>
<pre class="programlisting">
<span class="keyword">template</span><span class="special">&lt;</span>
<span class="keyword">typename</span> <span class="identifier">I</span>
<span class="special">&gt;</span>
<span class="keyword">struct</span> <span class="identifier">value_of</span>
<span class="special">{</span>
<span class="keyword">typedef</span> <span class="emphasis"><em>unspecified</em></span> <span class="identifier">type</span><span class="special">;</span>
<span class="special">};</span>
</pre>
<div class="table">
<a name="id962921"></a><p class="title"><b>Table 1.11. Parameters</b></p>
<table class="table" summary="Parameters">
<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">I</span></code>
</p>
</td>
<td>
<p>
Model of <a href="../concepts/forward_iterator.html" title="Forward
Iterator">Forward
Iterator</a>
</p>
</td>
<td>
<p>
Operation's argument
</p>
</td>
</tr></tbody>
</table>
</div>
<a name="fusion.iterators.metafunctions.value_of.expression_semantics"></a><h5>
<a name="id963012"></a>
<a href="value_of.html#fusion.iterators.metafunctions.value_of.expression_semantics">Expression
Semantics</a>
</h5>
<pre class="programlisting">
<a href="value_of.html" title="value_of"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_of</span></code></a><span class="special">&lt;</span><span class="identifier">I</span><span class="special">&gt;::</span><span class="identifier">type</span>
</pre>
<p>
<span class="bold"><strong>Return type</strong></span>: Any type
</p>
<p>
<span class="bold"><strong>Semantics</strong></span>: Returns the type stored in
a sequence at iterator position <code class="computeroutput"><span class="identifier">I</span></code>.
</p>
<a name="fusion.iterators.metafunctions.value_of.header"></a><h5>
<a name="id963113"></a>
<a href="value_of.html#fusion.iterators.metafunctions.value_of.header">Header</a>
</h5>
<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">iterator</span><span class="special">/</span><span class="identifier">value_of</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
</pre>
<a name="fusion.iterators.metafunctions.value_of.example"></a><h5>
<a name="id963197"></a>
<a href="value_of.html#fusion.iterators.metafunctions.value_of.example">Example</a>
</h5>
<pre class="programlisting">
<span class="keyword">typedef</span> <a href="../../sequences/containers/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span><span class="keyword">int</span><span class="special">&amp;,</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&amp;&gt;</span> <span class="identifier">vec</span><span class="special">;</span>
<span class="keyword">typedef</span> <a href="../../sequences/intrinsics/metafunctions/begin.html" title="begin"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">begin</span></code></a><span class="special">&lt;</span><span class="identifier">vec</span><span class="special">&gt;::</span><span class="identifier">type</span> <span class="identifier">first</span><span class="special">;</span>
<span class="keyword">typedef</span> <a href="next.html" title="next"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">next</span></code></a><span class="special">&lt;</span><span class="identifier">first</span><span class="special">&gt;::</span><span class="identifier">type</span> <span class="identifier">second</span><span class="special">;</span>
<span class="keyword">typedef</span> <a href="next.html" title="next"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">next</span></code></a><span class="special">&lt;</span><span class="identifier">second</span><span class="special">&gt;::</span><span class="identifier">type</span> <span class="identifier">third</span><span class="special">;</span>
<span class="identifier">BOOST_MPL_ASSERT</span><span class="special">((</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_same</span><span class="special">&lt;</span><a href="value_of.html" title="value_of"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_of</span></code></a><span class="special">&lt;</span><span class="identifier">first</span><span class="special">&gt;::</span><span class="identifier">type</span><span class="special">,</span> <span class="keyword">int</span><span class="special">&gt;));</span>
<span class="identifier">BOOST_MPL_ASSERT</span><span class="special">((</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_same</span><span class="special">&lt;</span><a href="value_of.html" title="value_of"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_of</span></code></a><span class="special">&lt;</span><span class="identifier">second</span><span class="special">&gt;::</span><span class="identifier">type</span><span class="special">,</span> <span class="keyword">int</span><span class="special">&amp;&gt;));</span>
<span class="identifier">BOOST_MPL_ASSERT</span><span class="special">((</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_same</span><span class="special">&lt;</span><a href="value_of.html" title="value_of"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_of</span></code></a><span class="special">&lt;</span><span class="identifier">third</span><span class="special">&gt;::</span><span class="identifier">type</span><span class="special">,</span> <span class="keyword">const</span> <span class="keyword">int</span><span class="special">&amp;&gt;));</span>
</pre>
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<td align="right"><small>Copyright © 2001-2007 Joel de Guzman, Dan Marsden, Tobias
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