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<a name="boost.proto.result_of.child_c"></a><div class="titlepage"></div>
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<h2><span class="refentrytitle">Struct template child_c</span></h2>
<p>boost::proto::result_of::child_c — A metafunction that returns the type of the <em class="replaceable"><code>N</code></em><sup>th</sup>
child of a Proto expression. </p>
</div>
<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: <<a class="link" href="../../../proto/reference.html#header.boost.proto.traits_hpp" title="Header <boost/proto/traits.hpp>">boost/proto/traits.hpp</a>>
</span><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <a class="link" href="../../../Expr.html" title="Concept Expr">Expr</a><span class="special">,</span> <span class="keyword">long</span> N<span class="special">></span>
<span class="keyword">struct</span> <a class="link" href="child_c.html" title="Struct template child_c">child_c</a> <span class="special">{</span>
<span class="comment">// <a class="link" href="child_c.html#boost.proto.result_of.child_ctypes">types</a></span>
<span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">Expr</span><span class="special">::</span><span class="identifier">proto_child0</span> <a class="link" href="child_c.html#boost.proto.result_of.child_c.value_type"><span class="identifier">value_type</span></a><span class="special">;</span>
<span class="keyword">typedef</span> <em class="replaceable"><code><span class="identifier">see</span><span class="special">-</span><span class="identifier">below</span></code></em> <a class="link" href="child_c.html#boost.proto.result_of.child_c.type"><span class="identifier">type</span></a><span class="special">;</span>
<span class="special">}</span><span class="special">;</span></pre></div>
<div class="refsect1">
<a name="idm45555179500688"></a><h2>Description</h2>
<p>
A metafunction that returns the type of the <em class="replaceable"><code>N</code></em><sup>th</sup>
child of a Proto expression. <code class="computeroutput">N</code> must be 0 or less than
<code class="computeroutput">Expr::proto_arity::value</code>.
</p>
<div class="refsect2">
<a name="idm45555179497648"></a><h3>
<a name="boost.proto.result_of.child_ctypes"></a><code class="computeroutput">child_c</code>
public
types</h3>
<div class="orderedlist"><ol class="orderedlist" type="1">
<li class="listitem">
<p>
<span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">Expr</span><span class="special">::</span><span class="identifier">proto_child0</span> <a name="boost.proto.result_of.child_c.value_type"></a><span class="identifier">value_type</span><span class="special">;</span></p>
<p>
The raw type of the <em class="replaceable"><code>N</code></em><sup>th</sup> child as it is stored
within <code class="computeroutput">Expr</code>. This may be a value or a reference.
</p>
</li>
<li class="listitem">
<p>
<span class="keyword">typedef</span> <em class="replaceable"><code><span class="identifier">see</span><span class="special">-</span><span class="identifier">below</span></code></em> <a name="boost.proto.result_of.child_c.type"></a><span class="identifier">type</span><span class="special">;</span></p>
<p>
If <code class="computeroutput">Expr</code> is not a reference type, <code class="computeroutput">type</code>
is computed as follows:
</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem"><p>
<code class="computeroutput">T const &</code> becomes <code class="computeroutput">T</code>
</p></li>
<li class="listitem"><p>
<code class="computeroutput">T &</code> becomes <code class="computeroutput">T</code>
</p></li>
<li class="listitem"><p>
<code class="computeroutput">T</code> becomes <code class="computeroutput">T</code>
</p></li>
</ul></div>
<p>
</p>
<p>
If <code class="computeroutput">Expr</code> is a non-const reference type, <code class="computeroutput">type</code>
is computed as follows:
</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem"><p>
<code class="computeroutput">T const &</code> becomes <code class="computeroutput">T const &</code>
</p></li>
<li class="listitem"><p>
<code class="computeroutput">T &</code> becomes <code class="computeroutput">T &</code>
</p></li>
<li class="listitem"><p>
<code class="computeroutput">T</code> becomes <code class="computeroutput">T &</code>
</p></li>
</ul></div>
<p>
</p>
<p>
If <code class="computeroutput">Expr</code> is a const reference type, <code class="computeroutput">type</code>
is computed as follows:
</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem"><p>
<code class="computeroutput">T const &</code> becomes <code class="computeroutput">T const &</code>
</p></li>
<li class="listitem"><p>
<code class="computeroutput">T &</code> becomes <code class="computeroutput">T &</code>
</p></li>
<li class="listitem"><p>
<code class="computeroutput">T</code> becomes <code class="computeroutput">T const &</code>
</p></li>
</ul></div>
<p>
</p>
</li>
</ol></div>
</div>
</div>
</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 © 2008 Eric Niebler<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>)
</p>
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