1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0.1 Transitional//EN"> 2 3<html> 4<head> 5<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> 6<title>Boost.Flyweight Documentation - Key-value flyweights reference</title> 7<link rel="stylesheet" href="../style.css" type="text/css"> 8<link rel="start" href="../index.html"> 9<link rel="prev" href="flyweight.html"> 10<link rel="up" href="index.html"> 11<link rel="next" href="tags.html"> 12</head> 13 14<body> 15<h1><img src="../../../../boost.png" alt="Boost logo" align= 16"middle" width="277" height="86">Key-value flyweights reference</h1> 17 18<div class="prev_link"><a href="flyweight.html"><img src="../prev.gif" alt="flyweight reference" border="0"><br> 19<code>flyweight</code> reference 20</a></div> 21<div class="up_link"><a href="index.html"><img src="../up.gif" alt="Boost.Flyweight reference" border="0"><br> 22Boost.Flyweight reference 23</a></div> 24<div class="next_link"><a href="tags.html"><img src="../next.gif" alt="tags" border="0"><br> 25Tags 26</a></div><br clear="all" style="clear: all;"> 27 28<hr> 29 30<h2>Contents</h2> 31 32<ul> 33 <li><a href="#key_extractor">Key extractors</a></li> 34 <li><a href="#key_value_fwd_synopsis">Header 35 <code>"boost/flyweight/key_value_fwd.hpp"</code> synopsis</a> 36 </li> 37 <li><a href="#synopsis">Header 38 <code>"boost/flyweight/key_value.hpp"</code> synopsis</a> 39 <ul> 40 <li><a href="#key_value_construct">Class template <code>key_value</code></a></li> 41 </ul> 42 </li> 43</ul> 44 45<h2><a name="key_extractor">Key extractors</a></h2> 46 47<p> 48Let <code>Key</code> be a type with some implicit equivalence relationship 49and <code>Value</code> a type constructible from <code>Key</code>. 50A <a href="https://boost.org/sgi/stl/DefaultConstructible.html"><code>Default 51Constructible</code></a> type <code>KeyFromValue</code> is said 52to be a key extractor from <code>Value</code> to <code>Key</code> if 53<ol> 54 <li><code>kfv(cv)</code> is defined and have type <code>const Key&</code>,</li> 55 <li><code>kfv(cv)</code> is equivalent to <code>kfv(Value(cv))</code>,</li> 56 <li><code>kfv(Value(k))</code> is equivalent to <code>k</code>,</li> 57</ol> 58for every <code>kfv</code> of type <code>const KeyFromValue</code>, 59<code>cv</code> of type <code>const Value</code> and 60<code>k</code> of type <code>Key</code>. 61</p> 62 63<h2><a name="key_value_fwd_synopsis">Header 64<a href="../../../../boost/flyweight/key_value_fwd.hpp"><code>"boost/flyweight/key_value_fwd.hpp"</code></a> synopsis</a></h2> 65 66<blockquote><pre> 67<span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span> 68 69<span class=keyword>namespace</span> <span class=identifier>flyweights</span><span class=special>{</span> 70 71<span class=keyword>struct</span> <span class=identifier>no_key_from_value</span><span class=special>;</span> 72 73<span class=keyword>template</span><span class=special><</span> 74 <span class=keyword>typename</span> <span class=identifier>Key</span><span class=special>,</span><span class=keyword>typename</span> <span class=identifier>Value</span><span class=special>,</span> 75 <span class=keyword>typename</span> <span class=identifier>KeyFromValue</span><span class=special>=</span><span class=identifier>no_key_from_value</span> 76<span class=special>></span> 77<span class=keyword>struct</span> <span class=identifier>key_value</span><span class=special>;</span> 78 79<span class=special>}</span> <span class=comment>// namespace boost::flyweights</span> 80 81<span class=special>}</span> <span class=comment>// namespace boost</span> 82</pre></blockquote> 83 84<h2><a name="synopsis">Header 85<a href="../../../../boost/flyweight/key_value.hpp"><code>"boost/flyweight/key_value.hpp"</code></a> synopsis</a></h2> 86 87<h3><a name="key_value_construct">Class template <code>key_value</code></a></h3> 88 89<p> 90In <a href="flyweight.html#flyweight"><code>flyweight</code></a> instantiations 91of the form <code>flyweight<T,...></code>, the associated 92<code>key_type</code> and <code>value_type</code> are both equal to <code>T</code>. 93Instantiations of the form <code>flyweight<key_value<Key,Value[,KeyFromValue]>,...></code> 94allow to specify these types separately. <code>Key</code> and <code>Value</code> 95must be different types. When provided, <code>KeyFromValue</code> 96must be a <a href="#key_extractor"><code>Key Extractor</code></a> from 97<code>Value</code> to <code>Key</code>. 98</p> 99 100<hr> 101 102<div class="prev_link"><a href="flyweight.html"><img src="../prev.gif" alt="flyweight reference" border="0"><br> 103<code>flyweight</code> reference 104</a></div> 105<div class="up_link"><a href="index.html"><img src="../up.gif" alt="Boost.Flyweight reference" border="0"><br> 106Boost.Flyweight reference 107</a></div> 108<div class="next_link"><a href="tags.html"><img src="../next.gif" alt="tags" border="0"><br> 109Tags 110</a></div><br clear="all" style="clear: all;"> 111 112<br> 113 114<p>Revised April 24th 2019</p> 115 116<p>© Copyright 2006-2019 Joaquín M López Muñoz. 117Distributed under the Boost Software 118License, Version 1.0. (See accompanying file <a href="../../../../LICENSE_1_0.txt"> 119LICENSE_1_0.txt</a> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt"> 120http://www.boost.org/LICENSE_1_0.txt</a>) 121</p> 122 123</body> 124</html> 125
