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>Function left</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.traits_hpp" title="Header <boost/proto/traits.hpp>"> 10<link rel="prev" href="value.html" title="Function value"> 11<link rel="next" href="right.html" title="Function right"> 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="value.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../proto/reference.html#header.boost.proto.traits_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="right.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 25</div> 26<div class="refentry"> 27<a name="boost.proto.left"></a><div class="titlepage"></div> 28<div class="refnamediv"> 29<h2><span class="refentrytitle">Function left</span></h2> 30<p>boost::proto::left — Return the left child of the specified binary Proto expression. </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.traits_hpp" title="Header <boost/proto/traits.hpp>">boost/proto/traits.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> 37 <span class="keyword">typename</span> <a class="link" href="result_of/left.html" title="Struct template left">proto::result_of::left</a><span class="special"><</span> <span class="identifier">Expr</span> <span class="special">&</span> <span class="special">></span><span class="special">::</span><span class="identifier">type</span> <span class="identifier">left</span><span class="special">(</span><span class="identifier">Expr</span> <span class="special">&</span> expr<span class="special">)</span><span class="special">;</span> 38<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> 39 <span class="keyword">typename</span> <a class="link" href="result_of/left.html" title="Struct template left">proto::result_of::left</a><span class="special"><</span> <span class="identifier">Expr</span> <span class="keyword">const</span> <span class="special">&</span> <span class="special">></span><span class="special">::</span><span class="identifier">type</span> 40 <span class="identifier">left</span><span class="special">(</span><span class="identifier">Expr</span> <span class="keyword">const</span> <span class="special">&</span> expr<span class="special">)</span><span class="special">;</span></pre></div> 41<div class="refsect1"> 42<a name="id-1.3.33.5.41.78.4"></a><h2>Description</h2> 43<p>Return the left child of the specified binary Proto expression. The child is returned by reference.</p> 44<div class="variablelist"><table border="0" class="variablelist compact"> 45<colgroup> 46<col align="left" valign="top"> 47<col> 48</colgroup> 49<tbody> 50<tr> 51<td><p><span class="term">Requires:</span></p></td> 52<td> 53<p> 54 <code class="computeroutput"><a class="link" href="is_expr.html" title="Struct template is_expr">proto::is_expr</a><Expr>::value</code> is 55 <code class="computeroutput">true</code>. 56 </p> 57<p> 58 <code class="computeroutput">2 == Expr::proto_arity::value</code> 59 </p> 60</td> 61</tr> 62<tr> 63<td><p><span class="term">Returns:</span></p></td> 64<td><p>A reference to the left child of <code class="computeroutput">expr</code>. 65 </p></td> 66</tr> 67<tr> 68<td><p><span class="term">Throws:</span></p></td> 69<td>Will not throw.</td> 70</tr> 71</tbody> 72</table></div> 73</div> 74</div> 75<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 76<td align="left"></td> 77<td align="right"><div class="copyright-footer">Copyright © 2008 Eric Niebler<p> 78 Distributed under the Boost Software License, Version 1.0. (See accompanying 79 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>) 80 </p> 81</div></td> 82</tr></table> 83<hr> 84<div class="spirit-nav"> 85<a accesskey="p" href="value.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../proto/reference.html#header.boost.proto.traits_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="right.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 86</div> 87</body> 88</html> 89
