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 env_var</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="../../../proto/reference.html#header.boost.proto.transform.env_hpp" title="Header <boost/proto/transform/env.hpp>"> 10<link rel="prev" href="has_env_var/result.html" title="Struct template result"> 11<link rel="next" href="env_var/result.html" title="Struct template result"> 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" 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class="refentry"> 27<a name="boost.proto.functional.env_var"></a><div class="titlepage"></div> 28<div class="refnamediv"> 29<h2><span class="refentrytitle">Struct template env_var</span></h2> 30<p>boost::proto::functional::env_var — 31 A unary <a class="link" href="../../../PolymorphicFunctionObject.html" title="Concept PolymorphicFunctionObject">PolymorphicFunctionObject</a> used for fetching the value 32 associated with a particular key in a transform environment. 33 </p> 34</div> 35<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> 36<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.env_hpp" title="Header <boost/proto/transform/env.hpp>">boost/proto/transform/env.hpp</a>> 37 38</span><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Key<span class="special">></span> 39<span class="keyword">struct</span> <a class="link" href="env_var.html" title="Struct template env_var">env_var</a> <span class="special">:</span> <span class="keyword"></span> <a class="link" href="../callable.html" title="Struct callable">proto::callable</a> <span class="special">{</span> 40 <span class="comment">// member classes/structs/unions</span> 41 <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Sig<span class="special">></span> 42 <span class="keyword">struct</span> <a class="link" href="env_var/result.html" title="Struct template result">result</a> <span class="special">{</span> 43 <span class="comment">// <a class="link" href="env_var/result.html#boost.proto.functional.env_var.resulttypes">types</a></span> 44 <span class="keyword">typedef</span> <em class="replaceable"><code><span class="identifier">see</span><span class="special">-</span><span class="identifier">below</span></code></em> <a class="link" href="env_var/result.html#boost.proto.functional.env_var.result.type"><span class="identifier">type</span></a><span class="special">;</span> 45 <span class="special">}</span><span class="special">;</span> 46 47 <span class="comment">// <a class="link" href="env_var.html#id-1_3_33_5_44_1_1_7_3_5-bb">public member functions</a></span> 48 <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Env<span class="special">></span> <em class="replaceable"><code><span class="identifier">see</span><span class="special">-</span><span class="identifier">below</span></code></em> <a class="link" href="env_var.html#id-1_3_33_5_44_1_1_7_3_5_1-bb"><span class="keyword">operator</span><span class="special">(</span><span class="special">)</span></a><span class="special">(</span><span class="identifier">Env</span> <span class="keyword">const</span> <span class="special">&</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> 49<span class="special">}</span><span class="special">;</span></pre></div> 50<div class="refsect1"> 51<a name="id-1.3.33.5.46.6.4"></a><h2>Description</h2> 52<div class="refsect2"> 53<a name="id-1.3.33.5.46.6.4.2"></a><h3> 54<a name="id-1_3_33_5_44_1_1_7_3_5-bb"></a><code class="computeroutput">env_var</code> public member functions</h3> 55<div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"> 56<pre class="literallayout"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> Env<span class="special">></span> <em class="replaceable"><code><span class="identifier">see</span><span class="special">-</span><span class="identifier">below</span></code></em> <a name="id-1_3_33_5_44_1_1_7_3_5_1-bb"></a><span class="keyword">operator</span><span class="special">(</span><span class="special">)</span><span class="special">(</span><span class="identifier">Env</span> <span class="keyword">const</span> <span class="special">&</span> e<span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre> 57<p> 58 This function behaves as follows: 59 </p> 60<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 61<li class="listitem"> 62 If <code class="computeroutput">Key</code> is <code class="computeroutput"><a class="link" href="../data_type.html" title="Struct data_type">proto::data_type</a></code>: 63 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; "> 64<li class="listitem"> 65 If <code class="computeroutput"><a class="link" href="../is_env.html" title="Struct template is_env">proto::is_env</a><Env>::value</code> is <code class="computeroutput">true</code>, 66 return <code class="computeroutput">e[<a class="link" href="../data.html" title="Global data">proto::data</a>]</code>. 67 </li> 68<li class="listitem"> 69 Otherwise, return <code class="computeroutput">e</code>. 70 </li> 71</ul></div> 72</li> 73<li class="listitem"> 74 Otherwise, return <code class="computeroutput">e[Key()]</code>. 75 </li> 76</ul></div> 77<p> 78 </p> 79<p> 80 See <code class="computeroutput"><a class="link" href="../env.html#id-1_3_33_5_44_1_1_3_3_1-bb">proto::env::operator[]</a></code> for additional information. 81 </p> 82</li></ol></div> 83</div> 84</div> 85</div> 86<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 87<td align="left"></td> 88<td align="right"><div class="copyright-footer">Copyright © 2008 Eric Niebler<p> 89 Distributed under the Boost Software License, Version 1.0. (See accompanying 90 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>) 91 </p> 92</div></td> 93</tr></table> 94<hr> 95<div class="spirit-nav"> 96<a accesskey="p" href="has_env_var/result.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../../proto/reference.html#header.boost.proto.transform.env_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="env_var/result.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 97</div> 98</body> 99</html> 100
