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diff --git a/doc/html/boost/proto/context/callable_context.html b/doc/html/boost/proto/context/callable_context.html new file mode 100755 index 0000000000..f5c9196a38 --- /dev/null +++ b/doc/html/boost/proto/context/callable_context.html @@ -0,0 +1,129 @@ +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> +<title>Struct template callable_context</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.context.callable_hpp" title="Header <boost/proto/context/callable.hpp>"> +<link rel="prev" href="callable_eval.html" title="Struct template callable_eval"> +<link rel="next" href="callable_context/eval.html" title="Struct template eval"> +</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="callable_eval.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../proto/reference.html#header.boost.proto.context.callable_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="callable_context/eval.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> +</div> +<div class="refentry"> +<a name="boost.proto.context.callable_context"></a><div class="titlepage"></div> +<div class="refnamediv"> +<h2><span class="refentrytitle">Struct template callable_context</span></h2> +<p>boost::proto::context::callable_context — An evaluation context adaptor that makes authoring a context a simple matter of + writing function overloads, rather then writing template specializations.</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.context.callable_hpp" title="Header <boost/proto/context/callable.hpp>">boost/proto/context/callable.hpp</a>> + +</span><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Context<span class="special">,</span> + <span class="keyword">typename</span> DefaultCtx <span class="special">=</span> <a class="link" href="default_context.html" title="Struct default_context">proto::context::default_context</a><span class="special">></span> +<span class="keyword">struct</span> <a class="link" href="callable_context.html" title="Struct template callable_context">callable_context</a> <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> ThisContext <span class="special">=</span> <span class="identifier">Context</span><span class="special">></span> + <span class="keyword">struct</span> <a class="link" href="callable_context/eval.html" title="Struct template eval">eval</a> <span class="special">:</span> <span class="keyword"></span> <em class="replaceable"><code>see-below</code></em> <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="id2888903"></a><h2>Description</h2> +<p> + <code class="computeroutput">proto::callable_context<></code> is a base class that + implements the context protocol by passing fanned-out expression nodes to the derived + context, making it easy to customize the handling of expression types by writing function + overloads. Only those expression types needing special handling require explicit handling. + All others are dispatched to a user-specified default context, + <code class="computeroutput">DefaultCtx</code>. + </p> +<p> + <code class="computeroutput">proto::callable_context<></code> is defined simply as: + </p> +<p> + </p> +<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Context</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">DefaultCtx</span> <span class="special">=</span> <span class="identifier">default_context</span><span class="special">></span> +<span class="keyword">struct</span> <span class="identifier">callable_context</span> <span class="special">{</span> + <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Expr</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">ThisContext</span> <span class="special">=</span> <span class="identifier">Context</span><span class="special">></span> + <span class="keyword">struct</span> <span class="identifier">eval</span> <span class="special">:</span> + <span class="identifier">mpl</span><span class="special">::</span><span class="identifier">if_</span><span class="special"><</span> + <span class="identifier">is_expr_handled_</span><span class="special"><</span><span class="identifier">Expr</span><span class="special">,</span> <span class="identifier">Context</span><span class="special">></span><span class="special">,</span> <span class="comment">// For exposition</span> + <a class="link" href="callable_eval.html" title="Struct template callable_eval">proto::context::callable_eval</a><span class="special"><</span><span class="identifier">Expr</span><span class="special">,</span> <span class="identifier">ThisContext</span><span class="special">></span><span class="special">,</span> + <span class="keyword">typename</span> <span class="identifier">DefaultCtx</span><span class="special">::</span><span class="keyword">template</span> <span class="identifier">eval</span><span class="special"><</span><span class="identifier">Expr</span><span class="special">,</span> <span class="identifier">Context</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="special">;</span> +<span class="special">}</span><span class="special">;</span></pre> +<p> + </p> +<p> + The Boolean metafunction <code class="computeroutput">is_expr_handled_<></code> uses + metaprogramming tricks to determine whether <code class="computeroutput">Context</code> has + an overloaded function call operator that accepts the fanned-out constituents of an + expression of type <code class="computeroutput">Expr</code>. If so, the handling of the + expression is dispatched to + <code class="computeroutput"><a class="link" href="callable_eval.html" title="Struct template callable_eval">proto::context::callable_eval<></a></code>. + If not, it is dispatched to the user-specified <code class="computeroutput">DefaultCtx</code>. + </p> +<p> + <span class="bold"><strong>Example:</strong></span> + </p> +<p> + </p> +<pre class="programlisting"><span class="comment">// An evaluation context that increments all</span> +<span class="comment">// integer terminals in-place.</span> +<span class="keyword">struct</span> <span class="identifier">increment_ints</span> <span class="special">:</span> + <a class="link" href="callable_context.html" title="Struct template callable_context">proto::context::callable_context</a><span class="special"><</span> + <span class="identifier">increment_ints</span> <span class="keyword">const</span> <span class="comment">// derived context</span> + <a class="link" href="null_context.html" title="Struct null_context">proto::context::null_context</a> <span class="keyword">const</span> <span class="comment">// fall-back context</span> + <span class="special">></span> +<span class="special">{</span> + <span class="keyword">typedef</span> <span class="keyword">void</span> <span class="identifier">result_type</span><span class="special">;</span> + + <span class="comment">// Handle int terminals here:</span> + <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">(</span><span class="special">)</span><span class="special">(</span><span class="identifier">proto</span><span class="special">::</span><span class="identifier">tag</span><span class="special">::</span><span class="identifier">terminal</span><span class="special">,</span> <span class="keyword">int</span> <span class="special">&</span><span class="identifier">i</span><span class="special">)</span> <span class="keyword">const</span> + <span class="special">{</span> + <span class="special">++</span><span class="identifier">i</span><span class="special">;</span> + <span class="special">}</span> +<span class="special">}</span><span class="special">;</span></pre> +<p> + </p> +<p> + With <code class="computeroutput">increment_ints</code>, we can do the following: + </p> +<p> + </p> +<pre class="programlisting"><a class="link" href="../literal.html" title="Struct template literal">proto::literal</a><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">,</span> <span class="identifier">j</span> <span class="special">=</span> <span class="number">10</span><span class="special">;</span> +<span class="identifier">proto</span><span class="special">::</span><span class="identifier">eval</span><span class="special">(</span> <span class="identifier">i</span> <span class="special">-</span> <span class="identifier">j</span> <span class="special">*</span> <span class="number">3</span><span class="special">.</span><span class="number">14</span><span class="special">,</span> <span class="identifier">increment_ints</span><span class="special">(</span><span class="special">)</span> <span class="special">)</span><span class="special">;</span> + +<span class="identifier">assert</span><span class="special">(</span> <span class="identifier">i</span><span class="special">.</span><span class="identifier">get</span><span class="special">(</span><span class="special">)</span> <span class="special">==</span> <span class="number">1</span> <span class="special">&&</span> <span class="identifier">j</span><span class="special">.</span><span class="identifier">get</span><span class="special">(</span><span class="special">)</span> <span class="special">==</span> <span class="number">11</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="callable_eval.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../proto/reference.html#header.boost.proto.context.callable_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="callable_context/eval.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> +</div> +</body> +</html> |