diff options
Diffstat (limited to 'doc/html/boost/proto/if_.html')
| -rwxr-xr-x | doc/html/boost/proto/if_.html | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/doc/html/boost/proto/if_.html b/doc/html/boost/proto/if_.html new file mode 100755 index 0000000000..7e23e54c20 --- /dev/null +++ b/doc/html/boost/proto/if_.html @@ -0,0 +1,132 @@ +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> +<title>Struct template if_</title> +<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css"> +<meta name="generator" content="DocBook XSL Stylesheets V1.76.1"> +<link rel="home" href="../../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> +<link rel="up" href="../../proto/reference.html#header.boost.proto.matches_hpp" title="Header <boost/proto/matches.hpp>"> +<link rel="prev" href="not_/impl.html" title="Struct template impl"> +<link rel="next" href="if_/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="not_/impl.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../proto/reference.html#header.boost.proto.matches_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="if_/impl.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> +</div> +<div class="refentry"> +<a name="boost.proto.if_"></a><div class="titlepage"></div> +<div class="refnamediv"> +<h2><span class="refentrytitle">Struct template if_</span></h2> +<p>boost::proto::if_ — Used to select one grammar or another based on the result of a compile-time Boolean. + When used as a transform, <code class="computeroutput">proto::if_<></code> selects between two + transforms based on a compile-time Boolean.</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.matches_hpp" title="Header <boost/proto/matches.hpp>">boost/proto/matches.hpp</a>> + +</span><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> If<span class="special">,</span> <span class="keyword">typename</span> Then <span class="special">=</span> <a class="link" href="_.html" title="Struct _">proto::_</a><span class="special">,</span> + <span class="keyword">typename</span> Else <span class="special">=</span> <a class="link" href="not_.html" title="Struct template not_">proto::not_</a><span class="special"><</span><a class="link" href="_.html" title="Struct _">proto::_</a><span class="special">></span> <span class="special">></span> +<span class="keyword">struct</span> <a class="link" href="if_.html" title="Struct template if_">if_</a> <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">if_</span><span class="special"><</span><span class="identifier">If</span><span class="special">,</span> <span class="identifier">Then</span><span class="special">,</span> <span class="identifier">Else</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="identifier">if_</span> <a name="boost.proto.if_.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="if_/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>< Expr, State, Data > <span class="special">{</span> + <span class="comment">// types</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> + <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">result_of</span><span class="special"><</span><a class="link" href="when.html" title="Struct template when">proto::when</a><span class="special"><</span><a class="link" href="_.html" title="Struct _">proto::_</a><span class="special">,</span> <span class="identifier">If</span><span class="special">></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><span class="special">,</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><a class="link" href="when.html" title="Struct template when">proto::when</a><span class="special"><</span><a class="link" href="_.html" title="Struct _">proto::_</a><span class="special">,</span> <span class="identifier">Then</span><span class="special">></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><span class="special">,</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><a class="link" href="when.html" title="Struct template when">proto::when</a><span class="special"><</span><a class="link" href="_.html" title="Struct _">proto::_</a><span class="special">,</span> <span class="identifier">Else</span><span class="special">></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> + <span class="special">></span><span class="special">::</span><span class="identifier">type</span> <a class="link" href="if_/impl.html#boost.proto.if_.impl.result_type"><span class="identifier">result_type</span></a><span class="special">;</span> + + <span class="comment">// <a class="link" href="if_/impl.html#id1505258-bb">public member functions</a></span> + <span class="identifier">result_type</span> <a class="link" href="if_/impl.html#id1505263-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="id2760520"></a><h2>Description</h2> +<p> + When <code class="computeroutput">proto::if_<If, Then, Else></code> is used as a grammar, + <code class="computeroutput">If</code> must be a Proto transform and + <code class="computeroutput">Then</code> and <code class="computeroutput">Else</code> must be grammars. + An expression type <code class="computeroutput">E</code> matches + <code class="computeroutput">proto::if_<If, Then, Else></code> if + <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 _">proto::_</a>, If>(E)>::type::value</code> + is <code class="computeroutput">true</code> and + <code class="computeroutput">E</code> matches <code class="computeroutput">Then</code>; or, if + <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 _">proto::_</a>, If>(E)>::type::value</code> + is <code class="computeroutput">false</code> and <code class="computeroutput">E</code> matches <code class="computeroutput">Else</code>. + </p> +<p> + The template parameter <code class="computeroutput">Then</code> defaults to <code class="computeroutput"><a class="link" href="_.html" title="Struct _">proto::_</a></code> + and <code class="computeroutput">Else</code> defaults to + <code class="computeroutput"><a class="link" href="not_.html" title="Struct template not_">proto::not_</a><<a class="link" href="_.html" title="Struct _">proto::_</a>></code>, + so an expression type <code class="computeroutput">E</code> will match + <code class="computeroutput">proto::if_<If></code> if and only if + <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 _">proto::_</a>, If>(E)>::type::value</code> + is <code class="computeroutput">true</code>. + </p> +<p> + </p> +<pre class="programlisting"><span class="comment">// A grammar that only matches integral terminals,</span> +<span class="comment">// using is_integral<> from Boost.Type_traits.</span> +<span class="keyword">struct</span> <span class="identifier">IsIntegral</span> <span class="special">:</span> + <a class="link" href="and_.html" title="Struct template and_">proto::and_</a><span class="special"><</span> + <a class="link" href="terminal.html" title="Struct template terminal">proto::terminal</a><span class="special"><</span><a class="link" href="_.html" title="Struct _">proto::_</a><span class="special">></span><span class="special">,</span> + <a class="link" href="if_.html" title="Struct template if_">proto::if_</a><span class="special"><</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_integral</span><span class="special"><</span><a class="link" href="_value.html" title="Struct _value">proto::_value</a><span class="special">></span><span class="special">(</span><span class="special">)</span><span class="special">></span> + <span class="special">></span> +<span class="special">{</span><span class="special">}</span><span class="special">;</span></pre> +<p> + </p> +<p> + When <code class="computeroutput">proto::if_<If, Then, Else></code> is used as a transform, + <code class="computeroutput">If</code>, <code class="computeroutput">Then</code> and + <code class="computeroutput">Else</code> must be Proto transforms. When applying the transform to + an expression <code class="computeroutput">E</code>, state <code class="computeroutput">S</code> and + data <code class="computeroutput">V</code>, if + <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 _">proto::_</a>, If>(E,S,V)>::type::value</code> + is <code class="computeroutput">true</code> then the <code class="computeroutput">Then</code> transform + is applied; otherwise the <code class="computeroutput">Else</code> transform is applied. + </p> +<pre class="programlisting"><span class="comment">// Match a terminal. If the terminal is integral, return</span> +<span class="comment">// mpl::true_; otherwise, return mpl::false_.</span> +<span class="keyword">struct</span> <span class="identifier">IsIntegral2</span> <span class="special">:</span> + <a class="link" href="when.html" title="Struct template when">proto::when</a><span class="special"><</span> + <a class="link" href="terminal.html" title="Struct template terminal">proto::terminal</a><span class="special"><</span><span class="identifier">_</span><span class="special">></span><span class="special">,</span> + <span class="identifier">proto</span><span class="special">::</span><span class="identifier">if_</span><span class="special"><</span> + <span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_integral</span><span class="special"><</span><a class="link" href="_value.html" title="Struct _value">proto::_value</a><span class="special">></span><span class="special">(</span><span class="special">)</span><span class="special">,</span> + <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span><span class="special">(</span><span class="special">)</span><span class="special">,</span> + <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">false_</span><span class="special">(</span><span class="special">)</span> + <span class="special">></span> + <span class="special">></span> +<span class="special">{</span><span class="special">}</span><span class="special">;</span></pre> +<p> + </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="not_/impl.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../proto/reference.html#header.boost.proto.matches_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="if_/impl.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> +</div> +</body> +</html> |