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 eval</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="../callable_context.html#id-1.3.33.5.56.5.4" title="Description"> 10<link rel="prev" href="../callable_context.html" title="Struct template callable_context"> 11<link rel="next" href="../default_eval.html" title="Struct template default_eval"> 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 href="../../../../../../index.html">Home</a></td> 17<td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td> 18<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 19<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 20<td align="center"><a href="../../../../../../more/index.htm">More</a></td> 21</tr></table> 22<hr> 23<div class="spirit-nav"> 24<a accesskey="p" href="../callable_context.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../callable_context.html#id-1.3.33.5.56.5.4"><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="../default_eval.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 25</div> 26<div class="refentry"> 27<a name="boost.proto.context.callable_context.eval"></a><div class="titlepage"></div> 28<div class="refnamediv"> 29<h2><span class="refentrytitle">Struct template eval</span></h2> 30<p>boost::proto::context::callable_context::eval</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.context.callable_hpp" title="Header <boost/proto/context/callable.hpp>">boost/proto/context/callable.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> ThisContext <span class="special">=</span> <span class="identifier">Context</span><span class="special">></span> 37<span class="keyword">struct</span> <a class="link" href="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> 38<span class="special">}</span><span class="special">;</span></pre></div> 39<div class="refsect1"> 40<a name="id-1.3.33.5.56.5.4.10.4"></a><h2>Description</h2> 41<p> 42 A BinaryFunction that accepts an <code class="computeroutput">Expr</code> and a 43 <code class="computeroutput">Context</code>, and either fans out the expression and passes 44 it to the context, or else hands off the expression to <code class="computeroutput">DefaultCtx</code>. 45 </p> 46<p> 47 If <code class="computeroutput">Context</code> is a <a class="link" href="../../../../PolymorphicFunctionObject.html" title="Concept PolymorphicFunctionObject">PolymorphicFunctionObject</a> 48 such that it can be invoked with the tag and children of <code class="computeroutput">Expr</code>, as 49 <code class="computeroutput">ctx(typename Expr::proto_tag(), child_c<0>(expr),... child_c<N>(expr))</code>, 50 then <code class="computeroutput">eval<Expr, ThisContext></code> inherits from 51 <code class="computeroutput"><a class="link" href="../callable_eval.html" title="Struct template callable_eval">proto::context::callable_eval</a><Expr, ThisContext></code>. 52 Otherwise, <code class="computeroutput">eval<Expr, ThisContext></code> inherits from 53 <code class="computeroutput">DefaultCtx::eval<Expr, Context></code>. 54 </p> 55</div> 56</div> 57<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 58<td align="left"></td> 59<td align="right"><div class="copyright-footer">Copyright © 2008 Eric Niebler<p> 60 Distributed under the Boost Software License, Version 1.0. (See accompanying 61 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>) 62 </p> 63</div></td> 64</tr></table> 65<hr> 66<div class="spirit-nav"> 67<a accesskey="p" href="../callable_context.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../callable_context.html#id-1.3.33.5.56.5.4"><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="../default_eval.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 68</div> 69</body> 70</html> 71
