1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Pairs</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="../tuple.html" title="Tuple"> 9<link rel="prev" href="class_template_tuple/relational_operators.html" title="Relational operators"> 10<link rel="next" href="../extension.html" title="Extension"> 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="class_template_tuple/relational_operators.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../tuple.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="../extension.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h3 class="title"> 27<a name="fusion.tuple.pairs"></a><a class="link" href="pairs.html" title="Pairs">Pairs</a> 28</h3></div></div></div> 29<h5> 30<a name="fusion.tuple.pairs.h0"></a> 31 <span class="phrase"><a name="fusion.tuple.pairs.description"></a></span><a class="link" href="pairs.html#fusion.tuple.pairs.description">Description</a> 32 </h5> 33<p> 34 The <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2002/n1403.pdf" target="_top">TR1 35 Tuple</a> interface is specified to provide uniform access to <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span></code> 36 as if it were a 2 element tuple. 37 </p> 38<h5> 39<a name="fusion.tuple.pairs.h1"></a> 40 <span class="phrase"><a name="fusion.tuple.pairs.specification"></a></span><a class="link" href="pairs.html#fusion.tuple.pairs.specification">Specification</a> 41 </h5> 42<pre class="programlisting"><span class="identifier">tuple_size</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">T1</span><span class="special">,</span> <span class="identifier">T2</span><span class="special">></span> <span class="special">>::</span><span class="identifier">value</span> 43</pre> 44<p> 45 <span class="bold"><strong>Type</strong></span>: An <a href="http://www.boost.org/libs/mpl/doc/refmanual/integral-constant.html" target="_top">MPL 46 Integral Constant</a> 47 </p> 48<p> 49 <span class="bold"><strong>Value</strong></span>: Returns 2, the number of elements 50 in a pair. 51 </p> 52<pre class="programlisting"><span class="identifier">tuple_element</span><span class="special"><</span><span class="number">0</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">T1</span><span class="special">,</span> <span class="identifier">T2</span><span class="special">></span> <span class="special">>::</span><span class="identifier">type</span> 53</pre> 54<p> 55 <span class="bold"><strong>Type</strong></span>: <code class="computeroutput"><span class="identifier">T1</span></code> 56 </p> 57<p> 58 <span class="bold"><strong>Value</strong></span>: Returns the type of the first element 59 of the pair 60 </p> 61<pre class="programlisting"><span class="identifier">tuple_element</span><span class="special"><</span><span class="number">1</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">T1</span><span class="special">,</span> <span class="identifier">T2</span><span class="special">></span> <span class="special">>::</span><span class="identifier">type</span> 62</pre> 63<p> 64 <span class="bold"><strong>Type</strong></span>: <code class="computeroutput"><span class="identifier">T2</span></code> 65 </p> 66<p> 67 <span class="bold"><strong>Value</strong></span>: Returns the type of the second element 68 of the pair 69 </p> 70<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">int</span> <span class="identifier">I</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">T2</span><span class="special">></span> 71<span class="identifier">P</span><span class="special">&</span> <span class="identifier">get</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">T1</span><span class="special">,</span> <span class="identifier">T2</span><span class="special">>&</span> <span class="identifier">pr</span><span class="special">);</span> 72 73<span class="keyword">template</span><span class="special"><</span><span class="keyword">int</span> <span class="identifier">I</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">T1</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">T2</span><span class="special">></span> 74<span class="keyword">const</span> <span class="identifier">P</span><span class="special">&</span> <span class="identifier">get</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">T1</span><span class="special">,</span> <span class="identifier">T2</span><span class="special">>&</span> <span class="identifier">pr</span><span class="special">);</span> 75</pre> 76<p> 77 <span class="bold"><strong>Type</strong></span>: If <code class="computeroutput"><span class="identifier">I</span> 78 <span class="special">==</span> <span class="number">0</span></code> 79 <code class="computeroutput"><span class="identifier">P</span></code> is <code class="computeroutput"><span class="identifier">T1</span></code>, 80 else if <code class="computeroutput"><span class="identifier">I</span> <span class="special">==</span> 81 <span class="number">1</span></code> <code class="computeroutput"><span class="identifier">P</span></code> 82 is <code class="computeroutput"><span class="identifier">T2</span></code> else the program is 83 ill-formed. 84 </p> 85<p> 86 [*Returns: <code class="computeroutput"><span class="identifier">pr</span><span class="special">.</span><span class="identifier">first</span></code> if <code class="computeroutput"><span class="identifier">I</span> 87 <span class="special">==</span> <span class="number">0</span></code> 88 else <code class="computeroutput"><span class="identifier">pr</span><span class="special">.</span><span class="identifier">second</span></code>. 89 </p> 90</div> 91<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 92<td align="left"></td> 93<td align="right"><div class="copyright-footer">Copyright © 2001-2006, 2011, 2012 Joel de Guzman, 94 Dan Marsden, Tobias Schwinger<p> 95 Distributed under the Boost Software License, Version 1.0. (See accompanying 96 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>) 97 </p> 98</div></td> 99</tr></table> 100<hr> 101<div class="spirit-nav"> 102<a accesskey="p" href="class_template_tuple/relational_operators.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../tuple.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="../extension.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 103</div> 104</body> 105</html> 106
