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25 <div class="refentry">
26 <a name="boost.proto.fold.impl"></a><div class="titlepage"></div>
27 <div class="refnamediv">
28 <h2><span class="refentrytitle">Struct template impl</span></h2>
29 <p>boost::proto::fold::impl</p>
31 <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
32 <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.transform.fold_hpp" title="Header <boost/proto/transform/fold.hpp>">boost/proto/transform/fold.hpp</a>>
35 <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">typename</span> State<span class="special">,</span> <span class="keyword">typename</span> Data<span class="special">></span>
36 <span class="keyword">struct</span> <a class="link" href="impl.html" title="Struct template impl">impl</a> <span class="special">:</span> <span class="keyword"></span> <a class="link" href="../transform_impl.html" title="Struct template transform_impl">proto::transform_impl</a><span class="special"><</span> <span class="identifier">Expr</span><span class="special">,</span> <span class="identifier">State</span><span class="special">,</span> <span class="identifier">Data</span> <span class="special">></span> <span class="special">{</span>
37 <span class="comment">// types</span>
38 <span class="keyword">typedef</span> <a class="link" href="../when.html" title="Struct template when">when</a><span class="special"><</span><a class="link" href="../_.html" title="Struct _">_</a><span class="special">,</span> <span class="identifier">Sequence</span><span class="special">></span> <a name="boost.proto.fold.impl.X"></a><span class="identifier">X</span><span class="special">;</span> <span class="comment">// For exposition only</span>
39 <span class="keyword">typedef</span> <a class="link" href="../when.html" title="Struct template when">when</a><span class="special"><</span><a class="link" href="../_.html" title="Struct _">_</a><span class="special">,</span> <span class="identifier">State0</span><span class="special">></span> <a name="boost.proto.fold.impl.Y"></a><span class="identifier">Y</span><span class="special">;</span> <span class="comment">// For exposition only</span>
40 <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">result_of</span><span class="special"><</span><span class="identifier">X</span><span class="special">(</span><span class="identifier">Expr</span><span class="special">,</span> <span class="identifier">State</span><span class="special">,</span> <span class="identifier">Data</span><span class="special">)</span><span class="special">></span><span class="special">::</span><span class="identifier">type</span> <a name="boost.proto.fold.impl.seq"></a><span class="identifier">seq</span><span class="special">;</span> <span class="comment">// A Fusion sequence, for exposition only</span>
41 <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">result_of</span><span class="special"><</span><span class="identifier">Y</span><span class="special">(</span><span class="identifier">Expr</span><span class="special">,</span> <span class="identifier">State</span><span class="special">,</span> <span class="identifier">Data</span><span class="special">)</span><span class="special">></span><span class="special">::</span><span class="identifier">type</span> <a name="boost.proto.fold.impl.state0"></a><span class="identifier">state0</span><span class="special">;</span> <span class="comment">// An initial state for the fold, for exposition only</span>
42 <span class="keyword">typedef</span> <span class="emphasis"><em><span class="identifier">unspecified</span></em></span> <a name="boost.proto.fold.impl.fun"></a><span class="identifier">fun</span><span class="special">;</span> <span class="comment">// <code class="computeroutput">fun(d)(s,e) == when<_,Fun>()(e,s,d)</code></span>
43 <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">fusion</span><span class="special">::</span><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">fold</span><span class="special"><</span><span class="identifier">seq</span><span class="special">,</span> <span class="identifier">state0</span><span class="special">,</span> <span class="identifier">fun</span><span class="special">></span><span class="special">::</span><span class="identifier">type</span> <a name="boost.proto.fold.impl.result_type"></a><span class="identifier">result_type</span><span class="special">;</span>
45 <span class="comment">// <a class="link" href="impl.html#idp207145088-bb">public member functions</a></span>
46 <span class="identifier">result_type</span> <a class="link" href="impl.html#idp207145648-bb"><span class="keyword">operator</span><span class="special">(</span><span class="special">)</span></a><span class="special">(</span><span class="keyword">typename</span> <span class="identifier">impl</span><span class="special">::</span><span class="identifier">expr_param</span><span class="special">,</span>
47 <span class="keyword">typename</span> <span class="identifier">impl</span><span class="special">::</span><span class="identifier">state_param</span><span class="special">,</span>
48 <span class="keyword">typename</span> <span class="identifier">impl</span><span class="special">::</span><span class="identifier">data_param</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
49 <span class="special">}</span><span class="special">;</span></pre></div>
50 <div class="refsect1">
51 <a name="idp389516880"></a><h2>Description</h2>
52 <div class="refsect2">
53 <a name="idp389517296"></a><h3>
54 <a name="idp207145088-bb"></a><code class="computeroutput">impl</code> public member functions</h3>
55 <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
56 <pre class="literallayout"><span class="identifier">result_type</span> <a name="idp207145648-bb"></a><span class="keyword">operator</span><span class="special">(</span><span class="special">)</span><span class="special">(</span><span class="keyword">typename</span> <span class="identifier">impl</span><span class="special">::</span><span class="identifier">expr_param</span> expr<span class="special">,</span>
57 <span class="keyword">typename</span> <span class="identifier">impl</span><span class="special">::</span><span class="identifier">state_param</span> state<span class="special">,</span>
58 <span class="keyword">typename</span> <span class="identifier">impl</span><span class="special">::</span><span class="identifier">data_param</span> data<span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>
60 Let <code class="computeroutput">seq</code> be
61 <code class="computeroutput"><code class="computeroutput"><a class="link" href="../when.html" title="Struct template when">when</a></code><<code class="computeroutput"><a class="link" href="../_.html" title="Struct _">_</a></code>, Sequence>()(expr, state, data)</code>,
62 let <code class="computeroutput">state0</code> be
63 <code class="computeroutput"><code class="computeroutput"><a class="link" href="../when.html" title="Struct template when">when</a></code><<code class="computeroutput"><a class="link" href="../_.html" title="Struct _">_</a></code>, State0>()(expr, state, data)</code>,
64 and let <code class="computeroutput">fun(data)</code> be an object such that
65 <code class="computeroutput">fun(data)(state, expr)</code> is equivalent to
66 <code class="computeroutput"><code class="computeroutput"><a class="link" href="../when.html" title="Struct template when">when</a></code><<code class="computeroutput"><a class="link" href="../_.html" title="Struct _">_</a></code>, Fun>()(expr, state, data)</code>. Then,
67 this function returns <code class="computeroutput">fusion::fold(seq, state0, fun(data))</code>.
69 <div class="variablelist"><table border="0" class="variablelist compact">
71 <col align="left" valign="top">
75 <td><p><span class="term">Parameters:</span></p></td>
76 <td><div class="variablelist"><table border="0" class="variablelist compact">
78 <col align="left" valign="top">
83 <td><p><span class="term"><code class="computeroutput">data</code></span></p></td>
84 <td><p>An arbitrary data </p></td>
87 <td><p><span class="term"><code class="computeroutput">expr</code></span></p></td>
88 <td><p>The current expression </p></td>
91 <td><p><span class="term"><code class="computeroutput">state</code></span></p></td>
92 <td><p>The current state </p></td>
102 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
103 <td align="left"></td>
104 <td align="right"><div class="copyright-footer">Copyright © 2008 Eric Niebler<p>
105 Distributed under the Boost Software License, Version 1.0. (See accompanying
106 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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