<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>pair</title> <link rel="stylesheet" href="../../../../../../doc/html/boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.75.1"> <link rel="home" href="../../index.html" title="Chapter 1. Fusion 2.0"> <link rel="up" href="../support.html" title="Support"> <link rel="prev" href="deduce_sequence.html" title="deduce_sequence"> <link rel="next" href="../iterator.html" title="Iterator"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table cellpadding="2" width="100%"><tr> <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td> <td align="center"><a href="../../../../../../index.html">Home</a></td> <td align="center"><a href="../../../../../libraries.htm">Libraries</a></td> <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> <td align="center"><a href="../../../../../../more/index.htm">More</a></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="deduce_sequence.html"><img src="../../../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../support.html"><img src="../../../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="../iterator.html"><img src="../../../../../../doc/html/images/next.png" alt="Next"></a> </div> <div class="section" title="pair"> <div class="titlepage"><div><div><h3 class="title"> <a name="fusion.support.pair"></a><a class="link" href="pair.html" title="pair">pair</a> </h3></div></div></div> <a name="fusion.support.pair.description"></a><h5> <a name="id618570"></a> <a class="link" href="pair.html#fusion.support.pair.description">Description</a> </h5> <p> Fusion <code class="computeroutput"><span class="identifier">pair</span></code> type is a half runtime pair. A half runtime pair is similar to a <a class="link" href="../adapted/std__pair.html" title="std::pair"><code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span></code></a>, but, unlike <a class="link" href="../adapted/std__pair.html" title="std::pair"><code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span></code></a>, the first type does not have data. It is used as elements in <a class="link" href="../container/map.html" title="map"><code class="computeroutput"><span class="identifier">map</span></code></a>s, for example. </p> <a name="fusion.support.pair.synopsis"></a><h5> <a name="id618637"></a> <a class="link" href="pair.html#fusion.support.pair.synopsis">Synopsis</a> </h5> <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">First</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Second</span><span class="special">></span> <span class="keyword">struct</span> <span class="identifier">pair</span><span class="special">;</span> <span class="keyword">namespace</span> <span class="identifier">result_of</span> <span class="special">{</span> <span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Pair</span><span class="special">></span> <span class="keyword">struct</span> <span class="identifier">first</span><span class="special">;</span> <span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Pair</span><span class="special">></span> <span class="keyword">struct</span> <span class="identifier">second</span><span class="special">;</span> <span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">First</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Second</span><span class="special">></span> <span class="keyword">struct</span> <span class="identifier">make_pair</span><span class="special">;</span> <span class="special">}</span> <span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">First</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Second</span><span class="special">></span> <span class="keyword">typename</span> <span class="identifier">result_of</span><span class="special">::</span><span class="identifier">make_pair</span><span class="special"><</span><span class="identifier">First</span><span class="special">,</span><span class="identifier">Second</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">make_pair</span><span class="special">(</span><span class="identifier">Second</span> <span class="keyword">const</span> <span class="special">&);</span> </pre> <a name="fusion.support.pair.template_parameters"></a><h5> <a name="id618934"></a> <a class="link" href="pair.html#fusion.support.pair.template_parameters">Template parameters</a> </h5> <div class="informaltable"><table class="table"> <colgroup> <col> <col> </colgroup> <thead><tr> <th> <p> Parameter </p> </th> <th> <p> Description </p> </th> </tr></thead> <tbody> <tr> <td> <p> First </p> </td> <td> <p> The first type. This is purely a type. No data is held. </p> </td> </tr> <tr> <td> <p> Second </p> </td> <td> <p> The second type. This contains data. </p> </td> </tr> </tbody> </table></div> <div class="variablelist" title="Notation"> <p class="title"><b>Notation</b></p> <dl> <dt><span class="term"><code class="computeroutput"><span class="identifier">P</span></code></span></dt> <dd><p> Fusion pair type </p></dd> <dt><span class="term"><code class="computeroutput"><span class="identifier">p</span></code>, <code class="computeroutput"><span class="identifier">p2</span></code></span></dt> <dd><p> Fusion pairs </p></dd> <dt><span class="term"><code class="computeroutput"><span class="identifier">F</span></code>, <code class="computeroutput"><span class="identifier">S</span></code></span></dt> <dd><p> Arbitrary types </p></dd> <dt><span class="term"><code class="computeroutput"><span class="identifier">s</span></code></span></dt> <dd><p> Value of type <code class="computeroutput"><span class="identifier">S</span></code> </p></dd> <dt><span class="term"><code class="computeroutput"><span class="identifier">o</span></code></span></dt> <dd><p> Output stream </p></dd> <dt><span class="term"><code class="computeroutput"><span class="identifier">i</span></code></span></dt> <dd><p> Input stream </p></dd> </dl> </div> <a name="fusion.support.pair.expression_semantics"></a><h5> <a name="id620244"></a> <a class="link" href="pair.html#fusion.support.pair.expression_semantics">Expression Semantics</a> </h5> <div class="informaltable"><table class="table"> <colgroup> <col> <col> </colgroup> <thead><tr> <th> <p> Expression </p> </th> <th> <p> Semantics </p> </th> </tr></thead> <tbody> <tr> <td> <p> <code class="computeroutput"><span class="identifier">P</span><span class="special">::</span><span class="identifier">first_type</span></code> </p> </td> <td> <p> The type of the first template parameter, <code class="computeroutput"><span class="identifier">F</span></code>, equivalent to <code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">first</span><span class="special"><</span><span class="identifier">P</span><span class="special">>::</span><span class="identifier">type</span></code>. </p> </td> </tr> <tr> <td> <p> <code class="computeroutput"><span class="identifier">P</span><span class="special">::</span><span class="identifier">second_type</span></code> </p> </td> <td> <p> The type of the second template parameter, <code class="computeroutput"><span class="identifier">S</span></code>, equivalent to <code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">second</span><span class="special"><</span><span class="identifier">P</span><span class="special">>::</span><span class="identifier">type</span></code>. </p> </td> </tr> <tr> <td> <p> <code class="computeroutput"><span class="identifier">P</span><span class="special">()</span></code> </p> </td> <td> <p> Default construction. </p> </td> </tr> <tr> <td> <p> <code class="computeroutput"><span class="identifier">P</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span></code> </p> </td> <td> <p> Construct a pair given value for the second type, <code class="computeroutput"><span class="identifier">s</span></code>. </p> </td> </tr> <tr> <td> <p> <code class="computeroutput"><span class="identifier">P</span><span class="special">(</span><span class="identifier">p2</span><span class="special">)</span></code> </p> </td> <td> <p> Copy constructs a pair from another pair, <code class="computeroutput"><span class="identifier">p2</span></code>. </p> </td> </tr> <tr> <td> <p> <code class="computeroutput"><span class="identifier">p</span><span class="special">.</span><span class="identifier">second</span></code> </p> </td> <td> <p> Get the data from <code class="computeroutput"><span class="identifier">p1</span></code>. </p> </td> </tr> <tr> <td> <p> <code class="computeroutput"><span class="identifier">p</span> <span class="special">=</span> <span class="identifier">p2</span></code> </p> </td> <td> <p> Assigns a pair, <code class="computeroutput"><span class="identifier">p1</span></code>, from another pair, <code class="computeroutput"><span class="identifier">p2</span></code>. </p> </td> </tr> <tr> <td> <p> make_pair<F>(s) </p> </td> <td> <p> Make a pair given the first type, <code class="computeroutput"><span class="identifier">F</span></code>, and a value for the second type, <code class="computeroutput"><span class="identifier">s</span></code>. The second type assumes the type of <code class="computeroutput"><span class="identifier">s</span></code> </p> </td> </tr> <tr> <td> <p> <code class="computeroutput"><span class="identifier">o</span> <span class="special"><<</span> <span class="identifier">p</span></code> </p> </td> <td> <p> Output <code class="computeroutput"><span class="identifier">p</span></code> to output stream, <code class="computeroutput"><span class="identifier">o</span></code>. </p> </td> </tr> <tr> <td> <p> <code class="computeroutput"><span class="identifier">i</span> <span class="special">>></span> <span class="identifier">p</span></code> </p> </td> <td> <p> Input <code class="computeroutput"><span class="identifier">p</span></code> from input stream, <code class="computeroutput"><span class="identifier">i</span></code>. </p> </td> </tr> <tr> <td> <p> <code class="computeroutput"><span class="identifier">p</span> <span class="special">==</span> <span class="identifier">p2</span></code> </p> </td> <td> <p> Tests two pairs for equality. </p> </td> </tr> <tr> <td> <p> <code class="computeroutput"><span class="identifier">p</span> <span class="special">!=</span> <span class="identifier">p2</span></code> </p> </td> <td> <p> Tests two pairs for inequality. </p> </td> </tr> </tbody> </table></div> <a name="fusion.support.pair.header"></a><h5> <a name="id620830"></a> <a class="link" href="pair.html#fusion.support.pair.header">Header</a> </h5> <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">support</span><span class="special">/</span><span class="identifier">pair</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> <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">pair</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> </pre> <a name="fusion.support.pair.example"></a><h5> <a name="id620938"></a> <a class="link" href="pair.html#fusion.support.pair.example">Example</a> </h5> <pre class="programlisting"><span class="identifier">pair</span><span class="special"><</span><span class="keyword">int</span><span class="special">,</span> <span class="keyword">char</span><span class="special">></span> <span class="identifier">p</span><span class="special">(</span><span class="char">'X'</span><span class="special">);</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">p</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">make_pair</span><span class="special"><</span><span class="keyword">int</span><span class="special">>(</span><span class="char">'X'</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> <span class="identifier">assert</span><span class="special">((</span><span class="identifier">p</span> <span class="special">==</span> <span class="identifier">make_pair</span><span class="special"><</span><span class="keyword">int</span><span class="special">>(</span><span class="char">'X'</span><span class="special">)));</span> </pre> </div> <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> <td align="left"></td> <td align="right"><div class="copyright-footer">Copyright © 2001-2007 Joel de Guzman, Dan Marsden, Tobias Schwinger<p> Distributed under the Boost Software License, Version 1.0. (See accompanying 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>) </p> </div></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="deduce_sequence.html"><img src="../../../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../support.html"><img src="../../../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="../iterator.html"><img src="../../../../../../doc/html/images/next.png" alt="Next"></a> </div> </body> </html>