1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Local Variables</title> 5<link rel="stylesheet" href="../../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../../index.html" title="Chapter 1. Phoenix 3.2.0"> 8<link rel="up" href="../scope.html" title="Scope"> 9<link rel="prev" href="../scope.html" title="Scope"> 10<link rel="next" href="let.html" title="let"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="../scope.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../scope.html"><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="let.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h4 class="title"> 27<a name="phoenix.modules.scope.local_variables"></a><a class="link" href="local_variables.html" title="Local Variables">Local Variables</a> 28</h4></div></div></div> 29<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">phoenix</span><span class="special">/</span><span class="identifier">scope</span><span class="special">/</span><span class="identifier">local_variable</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 30</pre> 31<p> 32 We use an instance of: 33 </p> 34<pre class="programlisting"><span class="identifier">expression</span><span class="special">::</span><span class="identifier">local_variable</span><span class="special"><</span><span class="identifier">Key</span><span class="special">>::</span><span class="identifier">type</span> 35</pre> 36<p> 37 to represent a local variable. The local variable acts as an imaginary 38 data-bin where a local, stack based data will be placed. <code class="computeroutput"><span class="identifier">Key</span></code> is an arbitrary type that is used 39 to identify the local variable. Example: 40 </p> 41<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">size_key</span><span class="special">;</span> 42<span class="identifier">expression</span><span class="special">::</span><span class="identifier">local_variable</span><span class="special"><</span><span class="identifier">size_key</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">size</span><span class="special">;</span> 43</pre> 44<p> 45 <span class="bold"><strong>Predefined Local Variables</strong></span> 46 </p> 47<p> 48 There are a few predefined instances of <code class="computeroutput"><span class="identifier">expression</span><span class="special">::</span><span class="identifier">local_variable</span><span class="special"><</span><span class="identifier">Key</span><span class="special">>::</span><span class="identifier">type</span></code> 49 named <code class="computeroutput"><span class="identifier">_a</span></code>..<code class="computeroutput"><span class="identifier">_z</span></code> that you can already use. To make 50 use of them, simply use the <code class="computeroutput"><span class="keyword">namespace</span> 51 <span class="identifier">boost</span><span class="special">::</span><span class="identifier">phoenix</span><span class="special">::</span><span class="identifier">local_names</span></code>: 52 </p> 53<pre class="programlisting"><span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">phoenix</span><span class="special">::</span><span class="identifier">local_names</span><span class="special">;</span> 54</pre> 55</div> 56<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 57<td align="left"></td> 58<td align="right"><div class="copyright-footer">Copyright © 2002-2005, 2010, 2014, 2015 Joel de Guzman, Dan Marsden, Thomas 59 Heller, John Fletcher<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="../scope.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../scope.html"><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="let.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 68</div> 69</body> 70</html> 71
