1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>value_of</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. Fusion 2.2"> 8<link rel="up" href="../metafunctions.html" title="Metafunctions"> 9<link rel="prev" href="../metafunctions.html" title="Metafunctions"> 10<link rel="next" href="deref.html" title="deref"> 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="../metafunctions.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../metafunctions.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="deref.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="fusion.iterator.metafunctions.value_of"></a><a class="link" href="value_of.html" title="value_of">value_of</a> 28</h4></div></div></div> 29<h6> 30<a name="fusion.iterator.metafunctions.value_of.h0"></a> 31 <span class="phrase"><a name="fusion.iterator.metafunctions.value_of.description"></a></span><a class="link" href="value_of.html#fusion.iterator.metafunctions.value_of.description">Description</a> 32 </h6> 33<p> 34 Returns the type stored at the position of an iterator. 35 </p> 36<h6> 37<a name="fusion.iterator.metafunctions.value_of.h1"></a> 38 <span class="phrase"><a name="fusion.iterator.metafunctions.value_of.synopsis"></a></span><a class="link" href="value_of.html#fusion.iterator.metafunctions.value_of.synopsis">Synopsis</a> 39 </h6> 40<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> 41 <span class="keyword">typename</span> <span class="identifier">I</span> 42 <span class="special">></span> 43<span class="keyword">struct</span> <span class="identifier">value_of</span> 44<span class="special">{</span> 45 <span class="keyword">typedef</span> <span class="emphasis"><em>unspecified</em></span> <span class="identifier">type</span><span class="special">;</span> 46<span class="special">};</span> 47</pre> 48<div class="table"> 49<a name="fusion.iterator.metafunctions.value_of.t0"></a><p class="title"><b>Table 1.11. Parameters</b></p> 50<div class="table-contents"><table class="table" summary="Parameters"> 51<colgroup> 52<col> 53<col> 54<col> 55</colgroup> 56<thead><tr> 57<th> 58 <p> 59 Parameter 60 </p> 61 </th> 62<th> 63 <p> 64 Requirement 65 </p> 66 </th> 67<th> 68 <p> 69 Description 70 </p> 71 </th> 72</tr></thead> 73<tbody><tr> 74<td> 75 <p> 76 <code class="computeroutput"><span class="identifier">I</span></code> 77 </p> 78 </td> 79<td> 80 <p> 81 Model of <a class="link" href="../concepts/forward_iterator.html" title="Forward Iterator">Forward 82 Iterator</a> 83 </p> 84 </td> 85<td> 86 <p> 87 Operation's argument 88 </p> 89 </td> 90</tr></tbody> 91</table></div> 92</div> 93<br class="table-break"><h6> 94<a name="fusion.iterator.metafunctions.value_of.h2"></a> 95 <span class="phrase"><a name="fusion.iterator.metafunctions.value_of.expression_semantics"></a></span><a class="link" href="value_of.html#fusion.iterator.metafunctions.value_of.expression_semantics">Expression 96 Semantics</a> 97 </h6> 98<pre class="programlisting"><a class="link" href="value_of.html" title="value_of"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_of</span></code></a><span class="special"><</span><span class="identifier">I</span><span class="special">>::</span><span class="identifier">type</span> 99</pre> 100<p> 101 <span class="bold"><strong>Return type</strong></span>: Any type 102 </p> 103<p> 104 <span class="bold"><strong>Semantics</strong></span>: Returns the type stored in 105 a sequence at iterator position <code class="computeroutput"><span class="identifier">I</span></code>. 106 </p> 107<h6> 108<a name="fusion.iterator.metafunctions.value_of.h3"></a> 109 <span class="phrase"><a name="fusion.iterator.metafunctions.value_of.header"></a></span><a class="link" href="value_of.html#fusion.iterator.metafunctions.value_of.header">Header</a> 110 </h6> 111<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">iterator</span><span class="special">/</span><span class="identifier">value_of</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 112<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">value_of</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 113</pre> 114<h6> 115<a name="fusion.iterator.metafunctions.value_of.h4"></a> 116 <span class="phrase"><a name="fusion.iterator.metafunctions.value_of.example"></a></span><a class="link" href="value_of.html#fusion.iterator.metafunctions.value_of.example">Example</a> 117 </h6> 118<pre class="programlisting"><span class="keyword">typedef</span> <a class="link" href="../../container/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a><span class="special"><</span><span class="keyword">int</span><span class="special">,</span><span class="keyword">int</span><span class="special">&,</span><span class="keyword">const</span> <span class="keyword">int</span><span class="special">&></span> <span class="identifier">vec</span><span class="special">;</span> 119<span class="keyword">typedef</span> <a class="link" href="../../sequence/intrinsic/metafunctions/begin.html" title="begin"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">begin</span></code></a><span class="special"><</span><span class="identifier">vec</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">first</span><span class="special">;</span> 120<span class="keyword">typedef</span> <a class="link" href="next.html" title="next"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">next</span></code></a><span class="special"><</span><span class="identifier">first</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">second</span><span class="special">;</span> 121<span class="keyword">typedef</span> <a class="link" href="next.html" title="next"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">next</span></code></a><span class="special"><</span><span class="identifier">second</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">third</span><span class="special">;</span> 122 123<span class="identifier">BOOST_MPL_ASSERT</span><span class="special">((</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_same</span><span class="special"><</span><a class="link" href="value_of.html" title="value_of"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_of</span></code></a><span class="special"><</span><span class="identifier">first</span><span class="special">>::</span><span class="identifier">type</span><span class="special">,</span> <span class="keyword">int</span><span class="special">>));</span> 124<span class="identifier">BOOST_MPL_ASSERT</span><span class="special">((</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_same</span><span class="special"><</span><a class="link" href="value_of.html" title="value_of"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_of</span></code></a><span class="special"><</span><span class="identifier">second</span><span class="special">>::</span><span class="identifier">type</span><span class="special">,</span> <span class="keyword">int</span><span class="special">&>));</span> 125<span class="identifier">BOOST_MPL_ASSERT</span><span class="special">((</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_same</span><span class="special"><</span><a class="link" href="value_of.html" title="value_of"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">value_of</span></code></a><span class="special"><</span><span class="identifier">third</span><span class="special">>::</span><span class="identifier">type</span><span class="special">,</span> <span class="keyword">const</span> <span class="keyword">int</span><span class="special">&>));</span> 126</pre> 127</div> 128<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 129<td align="left"></td> 130<td align="right"><div class="copyright-footer">Copyright © 2001-2006, 2011, 2012 Joel de Guzman, 131 Dan Marsden, Tobias Schwinger<p> 132 Distributed under the Boost Software License, Version 1.0. (See accompanying 133 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>) 134 </p> 135</div></td> 136</tr></table> 137<hr> 138<div class="spirit-nav"> 139<a accesskey="p" href="../metafunctions.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../metafunctions.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="deref.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 140</div> 141</body> 142</html> 143
