1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 2<html> 3<head> 4<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 5<title>Struct template impl</title> 6<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css"> 7<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 8<link rel="home" href="../../../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> 9<link rel="up" href="../fold.html#id-1.3.33.5.47.4.4" title="Description"> 10<link rel="prev" href="../fold.html" title="Struct template fold"> 11<link rel="next" href="../reverse_fold.html" title="Struct template reverse_fold"> 12</head> 13<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 14<table cellpadding="2" width="100%"><tr> 15<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td> 16<td align="center"><a 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29<h2><span class="refentrytitle">Struct template impl</span></h2> 30<p>boost::proto::fold::impl</p> 31</div> 32<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> 33<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>> 34 35</span> 36<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> 37<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> 38 <span class="comment">// types</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">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> 40 <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> 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">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> 42 <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> 43 <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> 44 <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 46 <span class="comment">// <a class="link" href="impl.html#id-1_3_33_5_45_2_1_1_5_9-bb">public member functions</a></span> 47 <span class="identifier">result_type</span> <a class="link" href="impl.html#id-1_3_33_5_45_2_1_1_5_9_1-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> 48 <span class="keyword">typename</span> <span class="identifier">impl</span><span class="special">::</span><span class="identifier">state_param</span><span class="special">,</span> 49 <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> 50<span class="special">}</span><span class="special">;</span></pre></div> 51<div class="refsect1"> 52<a name="id-1.3.33.5.47.4.4.3.4"></a><h2>Description</h2> 53<div class="refsect2"> 54<a name="id-1.3.33.5.47.4.4.3.4.2"></a><h3> 55<a name="id-1_3_33_5_45_2_1_1_5_9-bb"></a><code class="computeroutput">impl</code> public member functions</h3> 56<div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"> 57<pre class="literallayout"><span class="identifier">result_type</span> <a name="id-1_3_33_5_45_2_1_1_5_9_1-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> 58 <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> 59 <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<p> 61 Let <code class="computeroutput">seq</code> be 62 <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>, 63 let <code class="computeroutput">state0</code> be 64 <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>, 65 and let <code class="computeroutput">fun(data)</code> be an object such that 66 <code class="computeroutput">fun(data)(state, expr)</code> is equivalent to 67 <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, 68 this function returns <code class="computeroutput">fusion::fold(seq, state0, fun(data))</code>. 69 </p> 70<div class="variablelist"><table border="0" class="variablelist compact"> 71<colgroup> 72<col align="left" valign="top"> 73<col> 74</colgroup> 75<tbody><tr> 76<td><p><span class="term">Parameters:</span></p></td> 77<td><div class="variablelist"><table border="0" class="variablelist compact"> 78<colgroup> 79<col align="left" valign="top"> 80<col> 81</colgroup> 82<tbody> 83<tr> 84<td><p><span class="term"><code class="computeroutput">data</code></span></p></td> 85<td><p>An arbitrary data </p></td> 86</tr> 87<tr> 88<td><p><span class="term"><code class="computeroutput">expr</code></span></p></td> 89<td><p>The current expression </p></td> 90</tr> 91<tr> 92<td><p><span class="term"><code class="computeroutput">state</code></span></p></td> 93<td><p>The current state </p></td> 94</tr> 95</tbody> 96</table></div></td> 97</tr></tbody> 98</table></div> 99</li></ol></div> 100</div> 101</div> 102</div> 103<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 104<td align="left"></td> 105<td align="right"><div class="copyright-footer">Copyright © 2008 Eric Niebler<p> 106 Distributed under the Boost Software License, Version 1.0. (See accompanying 107 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>) 108 </p> 109</div></td> 110</tr></table> 111<hr> 112<div class="spirit-nav"> 113<a accesskey="p" href="../fold.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../fold.html#id-1.3.33.5.47.4.4"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../reverse_fold.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 114</div> 115</body> 116</html> 117
