1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>has_key</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="../functions.html" title="Functions"> 9<link rel="prev" href="at_c.html" title="at_c"> 10<link rel="next" href="at_key.html" title="at_key"> 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="at_c.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../functions.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="at_key.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h5 class="title"> 27<a name="fusion.sequence.intrinsic.functions.has_key"></a><a class="link" href="has_key.html" title="has_key">has_key</a> 28</h5></div></div></div> 29<h6> 30<a name="fusion.sequence.intrinsic.functions.has_key.h0"></a> 31 <span class="phrase"><a name="fusion.sequence.intrinsic.functions.has_key.description"></a></span><a class="link" href="has_key.html#fusion.sequence.intrinsic.functions.has_key.description">Description</a> 32 </h6> 33<p> 34 Returns a type convertible to <code class="computeroutput"><span class="keyword">bool</span></code> 35 that evaluates to <code class="computeroutput"><span class="keyword">true</span></code> if 36 the sequence contains an element associated with a Key, else, evaluates 37 to <code class="computeroutput"><span class="keyword">false</span></code>. 38 </p> 39<h6> 40<a name="fusion.sequence.intrinsic.functions.has_key.h1"></a> 41 <span class="phrase"><a name="fusion.sequence.intrinsic.functions.has_key.synopsis"></a></span><a class="link" href="has_key.html#fusion.sequence.intrinsic.functions.has_key.synopsis">Synopsis</a> 42 </h6> 43<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Key</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Sequence</span><span class="special">></span> 44<span class="keyword">typename</span> <a class="link" href="../metafunctions/has_key.html" title="has_key"><code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">has_key</span></code></a><span class="special"><</span><span class="identifier">Sequence</span><span class="special">,</span> <span class="identifier">Key</span><span class="special">>::</span><span class="identifier">type</span> 45<span class="identifier">has_key</span><span class="special">(</span><span class="identifier">Sequence</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">seq</span><span class="special">);</span> 46</pre> 47<h6> 48<a name="fusion.sequence.intrinsic.functions.has_key.h2"></a> 49 <span class="phrase"><a name="fusion.sequence.intrinsic.functions.has_key.parameters"></a></span><a class="link" href="has_key.html#fusion.sequence.intrinsic.functions.has_key.parameters">Parameters</a> 50 </h6> 51<div class="informaltable"><table class="table"> 52<colgroup> 53<col> 54<col> 55<col> 56</colgroup> 57<thead><tr> 58<th> 59 <p> 60 Parameter 61 </p> 62 </th> 63<th> 64 <p> 65 Requirement 66 </p> 67 </th> 68<th> 69 <p> 70 Description 71 </p> 72 </th> 73</tr></thead> 74<tbody> 75<tr> 76<td> 77 <p> 78 <code class="computeroutput"><span class="identifier">seq</span></code> 79 </p> 80 </td> 81<td> 82 <p> 83 Model of <a class="link" href="../../concepts/associative_sequence.html" title="Associative Sequence">Associative 84 Sequence</a> 85 </p> 86 </td> 87<td> 88 <p> 89 The sequence we wish to investigate. 90 </p> 91 </td> 92</tr> 93<tr> 94<td> 95 <p> 96 <code class="computeroutput"><span class="identifier">Key</span></code> 97 </p> 98 </td> 99<td> 100 <p> 101 Any type 102 </p> 103 </td> 104<td> 105 <p> 106 The queried key. 107 </p> 108 </td> 109</tr> 110</tbody> 111</table></div> 112<h6> 113<a name="fusion.sequence.intrinsic.functions.has_key.h3"></a> 114 <span class="phrase"><a name="fusion.sequence.intrinsic.functions.has_key.expression_semantics"></a></span><a class="link" href="has_key.html#fusion.sequence.intrinsic.functions.has_key.expression_semantics">Expression 115 Semantics</a> 116 </h6> 117<pre class="programlisting"><span class="identifier">has_key</span><span class="special"><</span><span class="identifier">Key</span><span class="special">>(</span><span class="identifier">seq</span><span class="special">);</span> 118</pre> 119<p> 120 <span class="bold"><strong>Return type</strong></span>: Convertible to <code class="computeroutput"><span class="keyword">bool</span></code>. 121 </p> 122<p> 123 <span class="bold"><strong>Semantics</strong></span>: Evaluates to <code class="computeroutput"><span class="keyword">true</span></code> if the sequence contains an element 124 associated with Key, else, evaluates to <code class="computeroutput"><span class="keyword">false</span></code>. 125 </p> 126<h6> 127<a name="fusion.sequence.intrinsic.functions.has_key.h4"></a> 128 <span class="phrase"><a name="fusion.sequence.intrinsic.functions.has_key.header"></a></span><a class="link" href="has_key.html#fusion.sequence.intrinsic.functions.has_key.header">Header</a> 129 </h6> 130<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">sequence</span><span class="special">/</span><span class="identifier">intrinsic</span><span class="special">/</span><span class="identifier">has_key</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 131<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">has_key</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 132</pre> 133<h6> 134<a name="fusion.sequence.intrinsic.functions.has_key.h5"></a> 135 <span class="phrase"><a name="fusion.sequence.intrinsic.functions.has_key.example"></a></span><a class="link" href="has_key.html#fusion.sequence.intrinsic.functions.has_key.example">Example</a> 136 </h6> 137<pre class="programlisting"><a class="link" href="../../../container/set.html" title="set"><code class="computeroutput"><span class="identifier">set</span></code></a><span class="special"><</span><span class="keyword">int</span><span class="special">,</span> <span class="keyword">char</span><span class="special">,</span> <span class="keyword">bool</span><span class="special">></span> <span class="identifier">s</span><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="char">'x'</span><span class="special">,</span> <span class="keyword">true</span><span class="special">);</span> 138<span class="identifier">assert</span><span class="special">(</span><span class="identifier">has_key</span><span class="special"><</span><span class="keyword">char</span><span class="special">>(</span><span class="identifier">s</span><span class="special">)</span> <span class="special">==</span> <span class="keyword">true</span><span class="special">);</span> 139</pre> 140</div> 141<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 142<td align="left"></td> 143<td align="right"><div class="copyright-footer">Copyright © 2001-2006, 2011, 2012 Joel de Guzman, 144 Dan Marsden, Tobias Schwinger<p> 145 Distributed under the Boost Software License, Version 1.0. (See accompanying 146 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>) 147 </p> 148</div></td> 149</tr></table> 150<hr> 151<div class="spirit-nav"> 152<a accesskey="p" href="at_c.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../functions.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="at_key.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 153</div> 154</body> 155</html> 156
