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