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  28 <div><h2 class="title">
  29 <a name="hash"></a>Chapter&#160;16.&#160;Boost.Functional/Hash</h2></div>
  30 <div><div class="author"><h3 class="author">
  31 <span class="firstname">Daniel</span> <span class="surname">James</span>
  32 </h3></div></div>
  33 <div><p class="copyright">Copyright &#169; 2005-2008 Daniel
  34       James</p></div>
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  36 <a name="hash.legal"></a><p>
  37         Distributed under the Boost Software License, Version 1.0. (See accompanying
  38         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>)
  39       </p>
  40 </div></div>
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  42 <div class="toc">
  43 <p><b>Table of Contents</b></p>
  44 <dl class="toc">
  45 <dt><span class="section"><a href="hash.html#hash.intro">Introduction</a></span></dt>
  46 <dt><span class="section"><a href="hash/tutorial.html">Tutorial</a></span></dt>
  47 <dt><span class="section"><a href="hash/custom.html">Extending boost::hash for a custom data type</a></span></dt>
  48 <dt><span class="section"><a href="hash/combine.html">Combining hash values</a></span></dt>
  49 <dt><span class="section"><a href="hash/portability.html">Portability</a></span></dt>
  50 <dt><span class="section"><a href="hash/disable.html">Disabling The Extensions</a></span></dt>
  51 <dt><span class="section"><a href="hash/changes.html">Change Log</a></span></dt>
  52 <dt><span class="section"><a href="hash/rationale.html">Rationale</a></span></dt>
  53 <dt><span class="section"><a href="hash/reference.html">Reference</a></span></dt>
  54 <dd><dl>
  55 <dt><span class="section"><a href="hash/reference.html#hash.reference.specification"></a></span></dt>
  56 <dt><span class="section"><a href="hash/reference.html#header.boost.functional.hash_hpp">Header &lt;boost/functional/hash.hpp&gt;</a></span></dt>
  57 </dl></dd>
  58 <dt><span class="section"><a href="hash/links.html">Links</a></span></dt>
  59 <dt><span class="section"><a href="hash/acknowledgements.html">Acknowledgements</a></span></dt>
  60 </dl>
  61 </div>
  62 <div class="section">
  63 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
  64 <a name="hash.intro"></a><a class="link" href="hash.html#hash.intro" title="Introduction">Introduction</a>
  65 </h2></div></div></div>
  66 <p>
  67       <code class="computeroutput"><a class="link" href="boost/hash.html" title="Struct template hash">boost::hash</a></code> is an implementation of
  68       the <a href="http://en.wikipedia.org/wiki/Hash_function" target="_top">hash function</a>
  69       object specified by the <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1836.pdf" target="_top">Draft
  70       Technical Report on C++ Library Extensions</a> (TR1). It is the default
  71       hash function for <a class="link" href="unordered.html" title="Chapter&#160;44.&#160;Boost.Unordered">Boost.Unordered</a>, <a class="link" href="intrusive/unordered_set_unordered_multiset.html" title="Semi-Intrusive unordered associative containers: unordered_set, unordered_multiset">Boost.Intrusive</a>'s
  72       unordered associative containers, and <a href="../../libs/multi_index/doc/index.html" target="_top">Boost.MultiIndex</a>'s
  73       hash indicies and <a href="../../libs/bimap/index.html" target="_top">Boost.Bimap</a>'s
  74       <code class="computeroutput"><span class="identifier">unordered_set_of</span></code>.
  75     </p>
  76 <p>
  77       As it is compliant with <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1836.pdf" target="_top">TR1</a>,
  78       it will work with:
  79     </p>
  80 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  81 <li class="listitem">
  82           integers
  83         </li>
  84 <li class="listitem">
  85           floats
  86         </li>
  87 <li class="listitem">
  88           pointers
  89         </li>
  90 <li class="listitem">
  91           strings
  92         </li>
  93 </ul></div>
  94 <p>
  95       It also implements the extension proposed by Peter Dimov in issue 6.18 of the
  96       <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1837.pdf" target="_top">Library
  97       Extension Technical Report Issues List</a> (page 63), this adds support
  98       for:
  99     </p>
 100 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
 101 <li class="listitem">
 102           arrays
 103         </li>
 104 <li class="listitem">
 105           <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span></code>
 106         </li>
 107 <li class="listitem">
 108           the standard containers.
 109         </li>
 110 <li class="listitem">
 111           extending <code class="computeroutput"><a class="link" href="boost/hash.html" title="Struct template hash">boost::hash</a></code> for custom
 112           types.
 113         </li>
 114 </ul></div>
 115 <div class="note"><table border="0" summary="Note">
 116 <tr>
 117 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../doc/src/images/note.png"></td>
 118 <th align="left">Note</th>
 119 </tr>
 120 <tr><td align="left" valign="top"><p>
 121         This hash function is designed to be used in containers based on the STL
 122         and is not suitable as a general purpose hash function. For more details
 123         see the <a class="link" href="hash/rationale.html" title="Rationale">rationale</a>.
 124       </p></td></tr>
 125 </table></div>
 126 </div>
 127 </div>
 128 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 129 <td align="left"><p><small>Last revised: April 17, 2017 at 02:30:32 GMT</small></p></td>
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