<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>Struct template impl</title> <link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.78.1"> <link rel="home" href="../../../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> <link rel="up" href="../make.html#idm45555170393232" title="Description"> <link rel="prev" href="../make.html" title="Struct template make"> <link rel="next" href="../pass_through.html" title="Struct template pass_through"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table cellpadding="2" width="100%"><tr> <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td> <td align="center"><a 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class="refentrytitle">Struct template impl</span></h2> <p>boost::proto::make::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="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>> </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">typename</span> State<span class="special">,</span> <span class="keyword">typename</span> Data<span class="special">></span> <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> <span class="comment">// <a class="link" href="impl.html#boost.proto.make.impltypes">types</a></span> <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> <span class="comment">// <a class="link" href="impl.html#idm45506983851760-bb">public member functions</a></span> <span class="identifier">result_type</span> <a class="link" href="impl.html#idm45506983851200-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> <span class="keyword">typename</span> <span class="identifier">impl</span><span class="special">::</span><span class="identifier">state_param</span><span class="special">,</span> <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> <span class="special">}</span><span class="special">;</span></pre></div> <div class="refsect1"> <a name="idm45555170346368"></a><h2>Description</h2> <div class="refsect2"> <a name="idm45555170345952"></a><h3> <a name="boost.proto.make.impltypes"></a><code class="computeroutput">impl</code> public types</h3> <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"> <p> <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> <p> <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 computed as follows: </p> <p> If <code class="computeroutput">T</code> is an <a class="link" href="../../../ObjectTransform.html" title="Concept ObjectTransform">ObjectTransform</a> of the form <code class="computeroutput">Object(A<sub>0</sub>,…A<sub>n</sub>)</code> or <code class="computeroutput">Object(A<sub>0</sub>,…A<sub>n</sub> ...)</code>, then let <code class="computeroutput">O</code> be the return type <code class="computeroutput">Object</code>. Otherwise, let <code class="computeroutput">O</code> be <code class="computeroutput">T</code>. The <code class="computeroutput">result_type</code> typedef is then computed as follows: </p> <p> </p> <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"><p> If <code class="computeroutput"><a class="link" href="../is_transform.html" title="Struct template is_transform">proto::is_transform</a><O>::value</code> is <code class="computeroutput">true</code>, then let the result type be <code class="computeroutput"> 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 </code>. Note that a substitution took place. </p></li> <li class="listitem"> If <code class="computeroutput">O</code> is a template like <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>, then the result type is calculated as follows: <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"><p> For each <code class="computeroutput">i</code> in <code class="computeroutput">[0,n]</code>, let <code class="computeroutput"> X<sub>i</sub>' </code> be <code class="computeroutput"> boost::result_of<<a class="link" href="../make.html" title="Struct template make">proto::make</a><X<sub>i</sub>>(Expr, State, Data)>::type </code> (which evaluates this procedure recursively). Note that a substitution took place. (In this case, Proto merely assumes that a substitution took place for the sake of compile-time efficiency. There would be no reason to use <code class="computeroutput"><a class="link" href="../noinvoke.html" title="Struct template noinvoke">proto::noinvoke<></a></code> otherwise.) </p></li> <li class="listitem"><p> The result type is <code class="computeroutput"> S<X<sub>0</sub>',…X<sub>n</sub>'> </code>. </p></li> </ul></div> </li> <li class="listitem"> If <code class="computeroutput">O</code> is a template like <code class="computeroutput">S<X<sub>0</sub>,…X<sub>n</sub>></code>, then the result type is calculated as follows: <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"><p> For each <code class="computeroutput">i</code> in <code class="computeroutput">[0,n]</code>, let <code class="computeroutput"> X<sub>i</sub>' </code> be <code class="computeroutput"> boost::result_of<<a class="link" href="../make.html" title="Struct template make">proto::make</a><X<sub>i</sub>>(Expr, State, Data)>::type </code> (which evaluates this procedure recursively). Note whether any substitutions took place during this operation. </p></li> <li class="listitem"><p> If any substitutions took place in the above step and <code class="computeroutput"> S<X<sub>0</sub>',…X<sub>n</sub>'> </code> has a nested <code class="computeroutput">type</code> typedef, the result type is <code class="computeroutput"> S<X<sub>0</sub>',…X<sub>n</sub>'>::type </code>. </p></li> <li class="listitem"><p> Otherwise, the result type is <code class="computeroutput"> S<X<sub>0</sub>',…X<sub>n</sub>'> </code>. </p></li> </ul></div> </li> <li class="listitem"> Otherwise, the result type is <code class="computeroutput">O</code>, and note that no substitution took place. </li> </ul></div> <p> </p> <p> Note that <code class="computeroutput"><a class="link" href="../when.html" title="Struct template when">proto::when<></a></code> is implemented in terms of <code class="computeroutput"><a class="link" href="../call.html" title="Struct template call">proto::call<></a></code> and <code class="computeroutput"><a class="link" href="../make.html" title="Struct template make">proto::make<></a></code>, so the above procedure is evaluated recursively. </p> </li></ol></div> </div> <div class="refsect2"> <a name="idm45555170286672"></a><h3> <a name="idm45506983851760-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="identifier">result_type</span> <a name="idm45506983851200-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> <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> <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> <p> <code class="computeroutput"> <code class="computeroutput"><a class="link" href="../make.html" title="Struct template make">proto::make</a></code><T>::impl<Expr,State,Data>::operator() </code> behaves as follows: </p> <p> </p> <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> <li class="listitem"> <p> If <code class="computeroutput">T</code> is of the form <code class="computeroutput">O(A<sub>0</sub>,…A<sub>n</sub>)</code>, then: </p> <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "> <li class="listitem"> <p> If <code class="computeroutput"> <code class="computeroutput"><a class="link" href="../is_aggregate.html" title="Struct template is_aggregate">proto::is_aggregate</a></code><result_type>::value </code> is <code class="computeroutput">true</code>, then construct and return an object <code class="computeroutput">that</code> as follows: </p> <pre class="programlisting">result_type that = { <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), … <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) };</pre> <p> </p> </li> <li class="listitem"> <p> Otherwise, construct and return an object <code class="computeroutput">that</code> as follows: </p> <pre class="programlisting">result_type that( <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), … <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) );</pre> <p> </p> </li> </ul></div> </li> <li class="listitem"> <p> If <code class="computeroutput">T</code> is of the form <code class="computeroutput">O(A<sub>0</sub>,…A<sub>n</sub> ...)</code>, 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>, 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> 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: </p> <pre class="programlisting">proto::make<T'>()(expr, state, data)</pre> <p> </p> </li> <li class="listitem"> <p> Otherwise, construct and return an object <code class="computeroutput">that</code> as follows: </p> <pre class="programlisting">result_type that = result_type();</pre> <p> </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> </div></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="../make.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../make.html#idm45555170393232"><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> </div> </body> </html>