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>Tutorial</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="../hash.html" title="Chapter 10. Boost.ContainerHash"> 10<link rel="prev" href="../hash.html" title="Chapter 10. Boost.ContainerHash"> 11<link rel="next" href="custom.html" title="Extending boost::hash for a custom data type"> 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="../hash.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../hash.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="custom.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> 25</div> 26<div class="section"> 27<div class="titlepage"><div><div><h2 class="title" style="clear: both"> 28<a name="hash.tutorial"></a><a class="link" href="tutorial.html" title="Tutorial">Tutorial</a> 29</h2></div></div></div> 30<p> 31 When using a hash index with <a href="../../../libs/multi_index/doc/index.html" target="_top">Boost.MultiIndex</a>, 32 you don't need to do anything to use <code class="computeroutput"><a class="link" href="../boost/hash.html" title="Struct template hash">boost::hash</a></code> 33 as it uses it by default. To find out how to use a user-defined type, read 34 the <a class="link" href="custom.html" title="Extending boost::hash for a custom data type">section on extending boost::hash for a custom 35 data type</a>. 36 </p> 37<p> 38 If your standard library supplies its own implementation of the unordered associative 39 containers and you wish to use <code class="computeroutput"><a class="link" href="../boost/hash.html" title="Struct template hash">boost::hash</a></code>, 40 just use an extra template parameter: 41 </p> 42<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">unordered_multiset</span><span class="special"><</span><span class="keyword">int</span><span class="special">,</span> <code class="computeroutput"><a class="link" href="../boost/hash.html" title="Struct template hash">boost::hash</a></code><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="special">></span> 43 <span class="identifier">set_of_ints</span><span class="special">;</span> 44 45<span class="identifier">std</span><span class="special">::</span><span class="identifier">unordered_set</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="keyword">int</span><span class="special">,</span> <span class="keyword">int</span><span class="special">>,</span> <code class="computeroutput"><a class="link" href="../boost/hash.html" title="Struct template hash">boost::hash</a></code><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="keyword">int</span><span class="special">,</span> <span class="keyword">int</span><span class="special">></span> <span class="special">></span> 46 <span class="identifier">set_of_pairs</span><span class="special">;</span> 47 48<span class="identifier">std</span><span class="special">::</span><span class="identifier">unordered_map</span><span class="special"><</span><span class="keyword">int</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">,</span> <code class="computeroutput"><a class="link" href="../boost/hash.html" title="Struct template hash">boost::hash</a></code><span class="special"><</span><span class="keyword">int</span><span class="special">></span> <span class="special">></span> <span class="identifier">map_int_to_string</span><span class="special">;</span> 49</pre> 50<p> 51 To use <code class="computeroutput"><a class="link" href="../boost/hash.html" title="Struct template hash">boost::hash</a></code> directly, create 52 an instance and call it as a function: 53 </p> 54<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><code class="computeroutput"><a class="link" href="reference.html#header.boost.container_hash.hash_hpp" title="Header <boost/container_hash/hash.hpp>">boost/container_hash/hash.hpp</a></code><span class="special">></span> 55 56<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> 57<span class="special">{</span> 58 <code class="computeroutput"><a class="link" href="../boost/hash.html" title="Struct template hash">boost::hash</a></code><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">></span> <span class="identifier">string_hash</span><span class="special">;</span> 59 60 <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">h</span> <span class="special">=</span> <span class="identifier">string_hash</span><span class="special">(</span><span class="string">"Hash me"</span><span class="special">);</span> 61<span class="special">}</span> 62</pre> 63<p> 64 For an example of generic use, here is a function to generate a vector containing 65 the hashes of the elements of a container: 66 </p> 67<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Container</span><span class="special">></span> 68<span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">></span> <span class="identifier">get_hashes</span><span class="special">(</span><span class="identifier">Container</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">)</span> 69<span class="special">{</span> 70 <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span><span class="special">></span> <span class="identifier">hashes</span><span class="special">;</span> 71 <span class="identifier">std</span><span class="special">::</span><span class="identifier">transform</span><span class="special">(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">end</span><span class="special">(),</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">back_inserter</span><span class="special">(</span><span class="identifier">hashes</span><span class="special">),</span> 72 <span class="identifier">boost</span><span class="special">::</span><span class="identifier">hash</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Container</span><span class="special">::</span><span class="identifier">value_type</span><span class="special">>());</span> 73 74 <span class="keyword">return</span> <span class="identifier">hashes</span><span class="special">;</span> 75<span class="special">}</span> 76</pre> 77</div> 78<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 79<td align="left"></td> 80<td align="right"><div class="copyright-footer">Copyright © 2005-2008 Daniel 81 James<p> 82 Distributed under the Boost Software License, Version 1.0. (See accompanying 83 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>) 84 </p> 85</div></td> 86</tr></table> 87<hr> 88<div class="spirit-nav"> 89<a accesskey="p" href="../hash.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../hash.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="custom.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> 90</div> 91</body> 92</html> 93
