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| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="fusion.support.category_of"></a><a class="link" href="category_of.html" title="category_of">category_of</a> |
| </h3></div></div></div> |
| <a name="fusion.support.category_of.description"></a><h5> |
| <a name="id838623"></a> |
| <a class="link" href="category_of.html#fusion.support.category_of.description">Description</a> |
| </h5> |
| <p> |
| A metafunction that establishes the conceptual classification of a particular |
| <a class="link" href="../sequence.html" title="Sequence">Sequence</a> or <a class="link" href="../iterator.html" title="Iterator">Iterator</a> |
| (see <a class="link" href="../iterator/concepts.html" title="Concepts">Iterator Concepts</a> and |
| <a class="link" href="../sequence/concepts.html" title="Concepts">Sequence Concepts</a>). |
| </p> |
| <a name="fusion.support.category_of.synopsis"></a><h5> |
| <a name="id838659"></a> |
| <a class="link" href="category_of.html#fusion.support.category_of.synopsis">Synopsis</a> |
| </h5> |
| <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">traits</span> |
| <span class="special">{</span> |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">category_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> |
| <span class="special">}</span> |
| </pre> |
| <a name="fusion.support.category_of.parameters"></a><h5> |
| <a name="id838752"></a> |
| <a class="link" href="category_of.html#fusion.support.category_of.parameters">Parameters</a> |
| </h5> |
| <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">T</span></code> |
| </p> |
| </td> |
| <td> |
| <p> |
| Any type |
| </p> |
| </td> |
| <td> |
| <p> |
| The type to query. |
| </p> |
| </td> |
| </tr></tbody> |
| </table></div> |
| <a name="fusion.support.category_of.expression_semantics"></a><h5> |
| <a name="id838840"></a> |
| <a class="link" href="category_of.html#fusion.support.category_of.expression_semantics">Expression |
| Semantics</a> |
| </h5> |
| <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">traits</span><span class="special">::</span><span class="identifier">category_of</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">category</span><span class="special">;</span> |
| </pre> |
| <p> |
| <span class="bold"><strong>Return type</strong></span>: |
| </p> |
| <p> |
| The return type is derived from one of: |
| </p> |
| <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">fusion</span> |
| <span class="special">{</span> |
| <span class="keyword">struct</span> <span class="identifier">incrementable_traversal_tag</span> <span class="special">{};</span> |
| |
| <span class="keyword">struct</span> <span class="identifier">single_pass_traversal_tag</span> |
| <span class="special">:</span> <span class="identifier">incrementable_traversal_tag</span> <span class="special">{};</span> |
| |
| <span class="keyword">struct</span> <span class="identifier">forward_traversal_tag</span> |
| <span class="special">:</span> <span class="identifier">single_pass_traversal_tag</span> <span class="special">{};</span> |
| |
| <span class="keyword">struct</span> <span class="identifier">bidirectional_traversal_tag</span> |
| <span class="special">:</span> <span class="identifier">forward_traversal_tag</span> <span class="special">{};</span> |
| |
| <span class="keyword">struct</span> <span class="identifier">random_access_traversal_tag</span> |
| <span class="special">:</span> <span class="identifier">bidirectional_traversal_tag</span> <span class="special">{};</span> |
| <span class="special">}}</span> |
| </pre> |
| <p> |
| And optionally from: |
| </p> |
| <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">fusion</span> |
| <span class="special">{</span> |
| <span class="keyword">struct</span> <span class="identifier">associative_tag</span> <span class="special">{};</span> |
| <span class="special">}}</span> |
| </pre> |
| <p> |
| <span class="bold"><strong>Semantics</strong></span>: Establishes the conceptual classification |
| of a particular <a class="link" href="../sequence.html" title="Sequence">Sequence</a> or <a class="link" href="../iterator.html" title="Iterator">Iterator</a>. |
| </p> |
| <a name="fusion.support.category_of.header"></a><h5> |
| <a name="id839676"></a> |
| <a class="link" href="category_of.html#fusion.support.category_of.header">Header</a> |
| </h5> |
| <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">support</span><span class="special">/</span><span class="identifier">category_of</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">category_of</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| </pre> |
| <a name="fusion.support.category_of.example"></a><h5> |
| <a name="id839784"></a> |
| <a class="link" href="category_of.html#fusion.support.category_of.example">Example</a> |
| </h5> |
| <pre class="programlisting"><span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_base_of</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">traits</span><span class="special">::</span><span class="identifier">category_of</span><span class="special"><</span><a class="link" href="../container/list.html" title="list"><code class="computeroutput"><span class="identifier">list</span></code></a><span class="special"><></span> <span class="special">>::</span><span class="identifier">type</span> <span class="identifier">list_category</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">traits</span><span class="special">::</span><span class="identifier">category_of</span><span class="special"><</span><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="special">>::</span><span class="identifier">type</span> <span class="identifier">vector_category</span><span class="special">;</span> |
| <span class="identifier">BOOST_MPL_ASSERT</span><span class="special">((</span> <span class="identifier">is_base_of</span><span class="special"><</span><span class="identifier">forward_traversal_tag</span><span class="special">,</span> <span class="identifier">list_category</span><span class="special">></span> <span class="special">));</span> |
| <span class="identifier">BOOST_MPL_ASSERT</span><span class="special">((</span> <span class="identifier">is_base_of</span><span class="special"><</span><span class="identifier">random_access_traversal_tag</span><span class="special">,</span> <span class="identifier">vector_category</span><span class="special">></span> <span class="special">));</span> |
| </pre> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"></td> |
| <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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