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<div class="refentry" title="Struct template impl">
<a name="boost.proto.when_Grammar,_R(A_)_id1272228.impl"></a><div class="titlepage"></div>
<div class="refnamediv">
<h2><span class="refentrytitle">Struct template impl</span></h2>
<p>boost::proto::when<Grammar, R(A...)>::impl</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="emphasis"><em>// In header: <<a class="link" href="../../../proto/reference.html#header.boost.proto.transform.when_hpp" title="Header <boost/proto/transform/when.hpp>">boost/proto/transform/when.hpp</a>>
</em></span>
<span class="bold"><strong>template</strong></span><<span class="bold"><strong>typename</strong></span> Expr, <span class="bold"><strong>typename</strong></span> State, <span class="bold"><strong>typename</strong></span> Data>
<span class="bold"><strong>struct</strong></span> <a class="link" href="impl.html" title="Struct template impl">impl</a> : <span class="bold"><strong></strong></span> <a class="link" href="../transform_impl.html" title="Struct template transform_impl">proto::transform_impl</a>< Expr, State, Data > {
<span class="emphasis"><em>// types</em></span>
<span class="bold"><strong>typedef</strong></span> <a class="link" href="../call.html" title="Struct template call">proto::call</a><R(A...)> <a name="boost.proto.when_Grammar,_R(A_)_id1272228.impl.call_"></a>call_; <span class="emphasis"><em>// For exposition only</em></span>
<span class="bold"><strong>typedef</strong></span> <a class="link" href="../make.html" title="Struct template make">proto::make</a><R(A...)> <a name="boost.proto.when_Grammar,_R(A_)_id1272228.impl.make_"></a>make_; <span class="emphasis"><em>// For exposition only</em></span>
<span class="bold"><strong>typedef</strong></span> <span class="bold"><strong>typename</strong></span> mpl::if_<<a class="link" href="../is_callable.html" title="Struct template is_callable">proto::is_callable</a><R>,call_,make_>::type <a name="boost.proto.when_Grammar,_R(A_)_id1272228.impl.which"></a>which; <span class="emphasis"><em>// For exposition only</em></span>
<span class="bold"><strong>typedef</strong></span> <span class="bold"><strong>typename</strong></span> boost::result_of<which(Expr, State, Data)>::type <a name="boost.proto.when_Grammar,_R(A_)_id1272228.impl.result_type"></a>result_type;
<span class="emphasis"><em>// <a class="link" href="impl.html#id1272429-bb">public member functions</a></em></span>
<span class="type">result_type</span> <a class="link" href="impl.html#id1272434-bb"><span class="bold"><strong>operator</strong></span>()</a>(<span class="bold"><strong>typename</strong></span> impl::expr_param,
<span class="bold"><strong>typename</strong></span> impl::state_param,
<span class="bold"><strong>typename</strong></span> impl::data_param) <span class="bold"><strong>const</strong></span>;
};</pre></div>
<div class="refsect1" title="Description">
<a name="id1678400"></a><h2>Description</h2>
<div class="refsect2" title="impl public member functions">
<a name="id1678404"></a><h3>
<a name="id1272429-bb"></a><code class="computeroutput">impl</code> public member functions</h3>
<div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
<pre class="literallayout"><span class="type">result_type</span> <a name="id1272434-bb"></a><span class="bold"><strong>operator</strong></span>()(<span class="bold"><strong>typename</strong></span> impl::expr_param expr,
<span class="bold"><strong>typename</strong></span> impl::state_param state,
<span class="bold"><strong>typename</strong></span> impl::data_param data) <span class="bold"><strong>const</strong></span>;</pre>
<p>
Evaluate <code class="computeroutput">R(A...)</code> as a transform either with
<code class="computeroutput"><code class="computeroutput"><a class="link" href="../call.html" title="Struct template call">proto::call<></a></code></code> or with
<code class="computeroutput"><code class="computeroutput"><a class="link" href="../make.html" title="Struct template make">proto::make<></a></code></code> depending
on whether <code class="computeroutput"><code class="computeroutput"><a class="link" href="../is_callable.html" title="Struct template is_callable">proto::is_callable</a></code><R>::value</code>
is <code class="computeroutput">true</code> or <code class="computeroutput">false</code>.
</p>
<div class="variablelist"><table border="0">
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<td><p><span class="term">Parameters:</span></p></td>
<td><div class="variablelist"><table border="0">
<col align="left" valign="top">
<tbody>
<tr>
<td><p><span class="term"><code class="computeroutput">data</code></span></p></td>
<td><p>An arbitrary data </p></td>
</tr>
<tr>
<td><p><span class="term"><code class="computeroutput">expr</code></span></p></td>
<td><p>The current expression </p></td>
</tr>
<tr>
<td><p><span class="term"><code class="computeroutput">state</code></span></p></td>
<td><p>The current state </p></td>
</tr>
</tbody>
</table></div></td>
</tr>
<tr>
<td><p><span class="term">Requires:</span></p></td>
<td><p>
<code class="computeroutput"><a class="link" href="../matches.html" title="Struct template matches">proto::matches</a><Expr, Grammar>::value</code>
is <code class="computeroutput">true</code>.
</p></td>
</tr>
<tr>
<td><p><span class="term">Returns:</span></p></td>
<td><p>
<code class="computeroutput">which()(expr, state, data)</code>
</p></td>
</tr>
</tbody>
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<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>)
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