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="../make.html#id-1.3.33.5.52.6.4" title="Description"> 10<link rel="prev" href="../make.html" title="Struct template make"> 11<link rel="next" href="../pass_through.html" title="Struct template pass_through"> 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::make::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.make_hpp" title="Header <boost/proto/transform/make.hpp>">boost/proto/transform/make.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">// <a class="link" href="impl.html#boost.proto.make.impltypes">types</a></span> 39 <span class="keyword">typedef</span> <span class="emphasis"><em><span class="identifier">see</span><span class="special">-</span><span class="identifier">below</span></em></span> <a class="link" href="impl.html#boost.proto.make.impl.result_type"><span class="identifier">result_type</span></a><span class="special">;</span> 40 41 <span class="comment">// <a class="link" href="impl.html#id-1_3_33_5_50_2_1_3_5_4-bb">public member functions</a></span> 42 <span class="identifier">result_type</span> <a class="link" href="impl.html#id-1_3_33_5_50_2_1_3_5_4_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> 43 <span class="keyword">typename</span> <span class="identifier">impl</span><span class="special">::</span><span class="identifier">state_param</span><span class="special">,</span> 44 <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> 45<span class="special">}</span><span class="special">;</span></pre></div> 46<div class="refsect1"> 47<a name="id-1.3.33.5.52.6.4.4.4"></a><h2>Description</h2> 48<div class="refsect2"> 49<a name="id-1.3.33.5.52.6.4.4.4.2"></a><h3> 50<a name="boost.proto.make.impltypes"></a><code class="computeroutput">impl</code> 51 public 52 types</h3> 53<div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"> 54<p> 55<span class="keyword">typedef</span> <span class="emphasis"><em><span class="identifier">see</span><span class="special">-</span><span class="identifier">below</span></em></span> <a name="boost.proto.make.impl.result_type"></a><span class="identifier">result_type</span><span class="special">;</span></p> 56<p> 57 <code class="computeroutput"><a class="link" href="../make.html" title="Struct template make">proto::make</a><T>::impl<Expr, State, Data>::result_type</code> is 58 computed as follows: 59 </p> 60<p> 61 If <code class="computeroutput">T</code> is an <a class="link" href="../../../ObjectTransform.html" title="Concept ObjectTransform">ObjectTransform</a> of the form 62 <code class="computeroutput">Object(A<sub>0</sub>,…A<sub>n</sub>)</code> or 63 <code class="computeroutput">Object(A<sub>0</sub>,…A<sub>n</sub> ...)</code>, 64 then let <code class="computeroutput">O</code> be the return type 65 <code class="computeroutput">Object</code>. Otherwise, let <code class="computeroutput">O</code> 66 be <code class="computeroutput">T</code>. The <code class="computeroutput">result_type</code> typedef is 67 then computed as follows: 68 </p> 69<p> 70 </p> 71<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 72<li class="listitem"><p> 73 If <code class="computeroutput"><a class="link" href="../is_transform.html" title="Struct template is_transform">proto::is_transform</a><O>::value</code> is 74 <code class="computeroutput">true</code>, then let the result type be 75 <code class="computeroutput"> 76 boost::result_of<<a class="link" href="../when.html" title="Struct template when">proto::when</a><<a class="link" href="../_.html" title="Struct _">_</a>, O>(Expr, State, Data)>::type 77 </code>. 78 Note that a substitution took place. 79 </p></li> 80<li class="listitem"> 81 If <code class="computeroutput">O</code> is a template like 82 <code class="computeroutput"><a class="link" href="../noinvoke.html" title="Struct template noinvoke">proto::noinvoke</a><S<X<sub>0</sub>,…X<sub>n</sub>> ></code>, 83 then the result type is calculated as follows: 84 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "> 85<li class="listitem"><p> 86 For each <code class="computeroutput">i</code> in 87 <code class="computeroutput">[0,n]</code>, let <code class="computeroutput"> 88 X<sub>i</sub>' 89 </code> be 90 <code class="computeroutput"> 91 boost::result_of<<a class="link" href="../make.html" title="Struct template make">proto::make</a><X<sub>i</sub>>(Expr, State, Data)>::type 92 </code> 93 (which evaluates this procedure recursively). Note that a substitution took place. (In this case, 94 Proto merely assumes that a substitution took place for the sake of compile-time efficiency. There 95 would be no reason to use <code class="computeroutput"><a class="link" href="../noinvoke.html" title="Struct template noinvoke">proto::noinvoke<></a></code> 96 otherwise.) 97 </p></li> 98<li class="listitem"><p> 99 The result type is 100 <code class="computeroutput"> 101 S<X<sub>0</sub>',…X<sub>n</sub>'> 102 </code>. 103 </p></li> 104</ul></div> 105</li> 106<li class="listitem"> 107 If <code class="computeroutput">O</code> is a template like 108 <code class="computeroutput">S<X<sub>0</sub>,…X<sub>n</sub>></code>, 109 then the result type is calculated as follows: 110 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "> 111<li class="listitem"><p> 112 For each <code class="computeroutput">i</code> in 113 <code class="computeroutput">[0,n]</code>, let <code class="computeroutput"> 114 X<sub>i</sub>' 115 </code> be 116 <code class="computeroutput"> 117 boost::result_of<<a class="link" href="../make.html" title="Struct template make">proto::make</a><X<sub>i</sub>>(Expr, State, Data)>::type 118 </code> 119 (which evaluates this procedure recursively). Note whether any substitutions took place during 120 this operation. 121 </p></li> 122<li class="listitem"><p> 123 If any substitutions took place in the above step and 124 <code class="computeroutput"> 125 S<X<sub>0</sub>',…X<sub>n</sub>'> 126 </code> has a nested 127 <code class="computeroutput">type</code> typedef, the result type is 128 <code class="computeroutput"> 129 S<X<sub>0</sub>',…X<sub>n</sub>'>::type 130 </code>. 131 </p></li> 132<li class="listitem"><p> 133 Otherwise, the result type is 134 <code class="computeroutput"> 135 S<X<sub>0</sub>',…X<sub>n</sub>'> 136 </code>. 137 </p></li> 138</ul></div> 139</li> 140<li class="listitem"> 141 Otherwise, the result type is <code class="computeroutput">O</code>, and note that no 142 substitution took place. 143 </li> 144</ul></div> 145<p> 146 </p> 147<p> 148 Note that <code class="computeroutput"><a class="link" href="../when.html" title="Struct template when">proto::when<></a></code> is implemented 149 in terms of <code class="computeroutput"><a class="link" href="../call.html" title="Struct template call">proto::call<></a></code> 150 and <code class="computeroutput"><a class="link" href="../make.html" title="Struct template make">proto::make<></a></code>, so the 151 above procedure is evaluated recursively. 152 </p> 153</li></ol></div> 154</div> 155<div class="refsect2"> 156<a name="id-1.3.33.5.52.6.4.4.4.3"></a><h3> 157<a name="id-1_3_33_5_50_2_1_3_5_4-bb"></a><code class="computeroutput">impl</code> public member functions</h3> 158<div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"> 159<pre class="literallayout"><span class="identifier">result_type</span> <a name="id-1_3_33_5_50_2_1_3_5_4_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> 160 <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> 161 <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> 162<p> 163 <code class="computeroutput"> 164 <code class="computeroutput"><a class="link" href="../make.html" title="Struct template make">proto::make</a></code><T>::impl<Expr,State,Data>::operator() 165 </code> 166 behaves as follows: 167 </p> 168<p> 169 </p> 170<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 171<li class="listitem"> 172<p> 173 If <code class="computeroutput">T</code> is of the form 174 <code class="computeroutput">O(A<sub>0</sub>,…A<sub>n</sub>)</code>, then: 175 </p> 176<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "> 177<li class="listitem"> 178<p> 179 If <code class="computeroutput"> 180 <code class="computeroutput"><a class="link" href="../is_aggregate.html" title="Struct template is_aggregate">proto::is_aggregate</a></code><result_type>::value 181 </code> is <code class="computeroutput">true</code>, then construct 182 and return an object <code class="computeroutput">that</code> as follows: 183 </p> 184<pre class="programlisting">result_type that = { 185 <code class="computeroutput"><a class="link" href="../when.html" title="Struct template when">proto::when</a></code><<code class="computeroutput"><a class="link" href="../_.html" title="Struct _">_</a></code>, A<sub>0</sub>>()(expr, state, data), 186 … 187 <code class="computeroutput"><a class="link" href="../when.html" title="Struct template when">proto::when</a></code><<code class="computeroutput"><a class="link" href="../_.html" title="Struct _">_</a></code>, A<sub>n</sub>>()(expr, state, data) 188};</pre> 189<p> 190 </p> 191</li> 192<li class="listitem"> 193<p> 194 Otherwise, construct 195 and return an object <code class="computeroutput">that</code> as follows: 196 </p> 197<pre class="programlisting">result_type that( 198 <code class="computeroutput"><a class="link" href="../when.html" title="Struct template when">proto::when</a></code><<code class="computeroutput"><a class="link" href="../_.html" title="Struct _">_</a></code>, A<sub>0</sub>>()(expr, state, data), 199 … 200 <code class="computeroutput"><a class="link" href="../when.html" title="Struct template when">proto::when</a></code><<code class="computeroutput"><a class="link" href="../_.html" title="Struct _">_</a></code>, A<sub>n</sub>>()(expr, state, data) 201);</pre> 202<p> 203 </p> 204</li> 205</ul></div> 206</li> 207<li class="listitem"> 208<p> 209 If <code class="computeroutput">T</code> is of the form 210 <code class="computeroutput">O(A<sub>0</sub>,…A<sub>n</sub> ...)</code>, 211 then let <code class="computeroutput">T'</code> be <code class="computeroutput">O(A<sub>0</sub>,…A<sub>n-1</sub>, <em class="replaceable"><code>S</code></em>)</code>, 212 where <em class="replaceable"><code>S</code></em> is a type sequence computed from the unpacking expression <code class="computeroutput">A<sub>n</sub></code> 213 as described in the reference for <code class="computeroutput"><code class="computeroutput"><a class="link" href="../pack.html" title="Struct pack">proto::pack</a></code></code>. Then, return: 214 </p> 215<pre class="programlisting">proto::make<T'>()(expr, state, data)</pre> 216<p> 217 </p> 218</li> 219<li class="listitem"> 220<p> 221 Otherwise, construct and return an object <code class="computeroutput">that</code> 222 as follows: </p> 223<pre class="programlisting">result_type that = result_type();</pre> 224<p> 225 </p> 226</li> 227</ul></div> 228<p> 229 </p> 230</li></ol></div> 231</div> 232</div> 233</div> 234<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 235<td align="left"></td> 236<td align="right"><div class="copyright-footer">Copyright © 2008 Eric Niebler<p> 237 Distributed under the Boost Software License, Version 1.0. (See accompanying 238 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>) 239 </p> 240</div></td> 241</tr></table> 242<hr> 243<div class="spirit-nav"> 244<a accesskey="p" href="../make.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../make.html#id-1.3.33.5.52.6.4"><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="../pass_through.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 245</div> 246</body> 247</html> 248
