| <html> |
| <head> |
| <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> |
| <title>Struct template when<Grammar, R(A...)></title> |
| <link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css"> |
| <meta name="generator" content="DocBook XSL Stylesheets V1.75.2"> |
| <link rel="home" href="../../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> |
| <link rel="up" href="../../proto/reference.html#header.boost.proto.transform.when_hpp" title="Header <boost/proto/transform/when.hpp>"> |
| <link rel="prev" href="when_Grammar__Fun_id1297061.html" title="Struct template when<Grammar, Fun *>"> |
| <link rel="next" href="when_Grammar__R_A___id1297144/impl.html" title="Struct template impl"> |
| </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 href="../../../../index.html">Home</a></td> |
| <td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td> |
| <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> |
| <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> |
| <td align="center"><a href="../../../../more/index.htm">More</a></td> |
| </tr></table> |
| <hr> |
| <div class="spirit-nav"> |
| <a accesskey="p" href="when_Grammar__Fun_id1297061.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../proto/reference.html#header.boost.proto.transform.when_hpp"><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="when_Grammar__R_A___id1297144/impl.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> |
| </div> |
| <div class="refentry"> |
| <a name="boost.proto.when_Grammar,_R(A_)_id1297144"></a><div class="titlepage"></div> |
| <div class="refnamediv"> |
| <h2><span class="refentrytitle">Struct template when<Grammar, R(A...)></span></h2> |
| <p>boost::proto::when<Grammar, R(A...)> — A grammar element and a <a class="link" href="../../PrimitiveTransform.html" title="Concept PrimitiveTransform">PrimitiveTransform</a> that associates a |
| transform with the grammar. </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.when_hpp" title="Header <boost/proto/transform/when.hpp>">boost/proto/transform/when.hpp</a>> |
| |
| </span><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Grammar<span class="special">,</span> <span class="keyword">typename</span> R<span class="special">,</span> <span class="keyword">typename</span><span class="special">...</span> A<span class="special">></span> |
| <span class="keyword">struct</span> <a class="link" href="when_Grammar__R_A___id1297144.html" title="Struct template when<Grammar, R(A...)>">when</a><span class="special"><</span><span class="identifier">Grammar</span><span class="special">,</span> <span class="identifier">R</span><span class="special">(</span><span class="identifier">A</span><span class="special">...</span><span class="special">)</span><span class="special">></span> <span class="special">:</span> <span class="keyword"></span> <a class="link" href="transform.html" title="Struct template transform">proto::transform</a><span class="special"><</span> <span class="identifier">when</span><span class="special"><</span><span class="identifier">Grammar</span><span class="special">,</span> <span class="identifier">R</span><span class="special">(</span><span class="identifier">A</span><span class="special">...</span><span class="special">)</span><span class="special">></span> <span class="special">></span> <span class="special">{</span> |
| <span class="comment">// types</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">Grammar</span><span class="special">::</span><span class="identifier">proto_grammar</span> <a name="boost.proto.when_Grammar,_R(A_)_id1297144.proto_grammar"></a><span class="identifier">proto_grammar</span><span class="special">;</span> |
| |
| <span class="comment">// member classes/structs/unions</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="when_Grammar__R_A___id1297144/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">// types</span> |
| <span class="keyword">typedef</span> <a class="link" href="call.html" title="Struct template call">proto::call</a><span class="special"><</span><span class="identifier">R</span><span class="special">(</span><span class="identifier">A</span><span class="special">...</span><span class="special">)</span><span class="special">></span> <a class="link" href="when_Grammar__R_A___id1297144/impl.html#boost.proto.when_Grammar,_R(A_)_id1297144.impl.call_"><span class="identifier">call_</span></a><span class="special">;</span> <span class="comment">// For exposition only</span> |
| <span class="keyword">typedef</span> <a class="link" href="make.html" title="Struct template make">proto::make</a><span class="special"><</span><span class="identifier">R</span><span class="special">(</span><span class="identifier">A</span><span class="special">...</span><span class="special">)</span><span class="special">></span> <a class="link" href="when_Grammar__R_A___id1297144/impl.html#boost.proto.when_Grammar,_R(A_)_id1297144.impl.make_"><span class="identifier">make_</span></a><span class="special">;</span> <span class="comment">// For exposition only</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">if_</span><span class="special"><</span><a class="link" href="is_callable.html" title="Struct template is_callable">proto::is_callable</a><span class="special"><</span><span class="identifier">R</span><span class="special">></span><span class="special">,</span><span class="identifier">call_</span><span class="special">,</span><span class="identifier">make_</span><span class="special">></span><span class="special">::</span><span class="identifier">type</span> <a class="link" href="when_Grammar__R_A___id1297144/impl.html#boost.proto.when_Grammar,_R(A_)_id1297144.impl.which"><span class="identifier">which</span></a><span class="special">;</span> <span class="comment">// For exposition only</span> |
| <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">which</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 class="link" href="when_Grammar__R_A___id1297144/impl.html#boost.proto.when_Grammar,_R(A_)_id1297144.impl.result_type"><span class="identifier">result_type</span></a><span class="special">;</span> |
| |
| <span class="comment">// <a class="link" href="when_Grammar__R_A___id1297144/impl.html#id1297345-bb">public member functions</a></span> |
| <span class="identifier">result_type</span> <a class="link" href="when_Grammar__R_A___id1297144/impl.html#id1297350-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> |
| <span class="special">}</span><span class="special">;</span></pre></div> |
| <div class="refsect1"> |
| <a name="id2448986"></a><h2>Description</h2> |
| <p> |
| Use <code class="computeroutput">proto::when<></code> to override a grammar's default |
| transform with a custom transform. It is for use when composing larger transforms by associating |
| smaller transforms with individual rules in your grammar. |
| </p> |
| <p> |
| The <code class="computeroutput">when<G, R(A...)></code> form accepts either a |
| <a class="link" href="../../CallableTransform.html" title="Concept CallableTransform">CallableTransform</a> or an <a class="link" href="../../ObjectTransform.html" title="Concept ObjectTransform">ObjectTransform</a> as its |
| second parameter. <code class="computeroutput">proto::when<></code> uses |
| <code class="computeroutput"><a class="link" href="is_callable.html" title="Struct template is_callable">proto::is_callable</a><R>::value</code> to |
| distinguish between the two, and uses |
| <code class="computeroutput"><a class="link" href="call.html" title="Struct template call">proto::call<></a></code> to evaluate |
| <a class="link" href="../../CallableTransform.html" title="Concept CallableTransform">CallableTransform</a>s and |
| <code class="computeroutput"><a class="link" href="make.html" title="Struct template make">proto::make<></a></code> to evaluate |
| <a class="link" href="../../ObjectTransform.html" title="Concept ObjectTransform">ObjectTransform</a>s. |
| </p> |
| </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="when_Grammar__Fun_id1297061.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../proto/reference.html#header.boost.proto.transform.when_hpp"><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="when_Grammar__R_A___id1297144/impl.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> |
| </div> |
| </body> |
| </html> |