<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>empty</title> <link rel="stylesheet" href="../../../../../../../../doc/html/boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.75.1"> <link rel="home" href="../../../../index.html" title="Chapter 1. Fusion 2.0"> <link rel="up" href="../metafunctions.html" title="Metafunctions"> <link rel="prev" href="end.html" title="end"> <link rel="next" href="front.html" title="front"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table cellpadding="2" width="100%"><tr> <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../../boost.png"></td> <td align="center"><a href="../../../../../../../../index.html">Home</a></td> <td align="center"><a href="../../../../../../../libraries.htm">Libraries</a></td> <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> <td align="center"><a href="../../../../../../../../more/index.htm">More</a></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="end.html"><img src="../../../../../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../metafunctions.html"><img src="../../../../../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="front.html"><img src="../../../../../../../../doc/html/images/next.png" alt="Next"></a> </div> <div class="section" title="empty"> <div class="titlepage"><div><div><h5 class="title"> <a name="fusion.sequence.intrinsic.metafunctions.empty"></a><a class="link" href="empty.html" title="empty">empty</a> </h5></div></div></div> <a name="fusion.sequence.intrinsic.metafunctions.empty.description"></a><h6> <a name="id667397"></a> <a class="link" href="empty.html#fusion.sequence.intrinsic.metafunctions.empty.description">Description</a> </h6> <p> Returns the result type of <a class="link" href="../functions/empty.html" title="empty"><code class="computeroutput"><span class="identifier">empty</span></code></a>. </p> <a name="fusion.sequence.intrinsic.metafunctions.empty.synopsis"></a><h6> <a name="id667425"></a> <a class="link" href="empty.html#fusion.sequence.intrinsic.metafunctions.empty.synopsis">Synopsis</a> </h6> <pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Seq</span><span class="special">></span> <span class="keyword">struct</span> <span class="identifier">empty</span> <span class="special">{</span> <span class="keyword">typedef</span> <span class="emphasis"><em>unspecified</em></span> <span class="identifier">type</span><span class="special">;</span> <span class="special">};</span> </pre> <div class="table"> <a name="id667495"></a><p class="title"><b>Table 1.25. Parameters</b></p> <div class="table-contents"><table class="table" summary="Parameters"> <colgroup> <col> <col> <col> </colgroup> <thead><tr> <th> <p> Parameter </p> </th> <th> <p> Requirement </p> </th> <th> <p> Description </p> </th> </tr></thead> <tbody><tr> <td> <p> <code class="computeroutput"><span class="identifier">Seq</span></code> </p> </td> <td> <p> A model of <a class="link" href="../../concepts/forward_sequence.html" title="Forward Sequence">Forward Sequence</a> </p> </td> <td> <p> Argument sequence </p> </td> </tr></tbody> </table></div> </div> <br class="table-break"><a name="fusion.sequence.intrinsic.metafunctions.empty.expression_semantics"></a><h6> <a name="id667577"></a> <a class="link" href="empty.html#fusion.sequence.intrinsic.metafunctions.empty.expression_semantics">Expression Semantics</a> </h6> <pre class="programlisting"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">empty</span><span class="special"><</span><span class="identifier">Seq</span><span class="special">>::</span><span class="identifier">type</span> </pre> <p> <span class="bold"><strong>Return type</strong></span>: An <a href="http://www.boost.org/libs/mpl/doc/refmanual/integral-constant.html" target="_top">MPL Integral Constant</a> </p> <p> <span class="bold"><strong>Semantics</strong></span>: Returns <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span></code> if <code class="computeroutput"><span class="identifier">Seq</span></code> has zero elements, <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">false_</span></code> otherwise. </p> <a name="fusion.sequence.intrinsic.metafunctions.empty.header"></a><h6> <a name="id667677"></a> <a class="link" href="empty.html#fusion.sequence.intrinsic.metafunctions.empty.header">Header</a> </h6> <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> <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> </pre> <a name="fusion.sequence.intrinsic.metafunctions.empty.example"></a><h6> <a name="id667793"></a> <a class="link" href="empty.html#fusion.sequence.intrinsic.metafunctions.empty.example">Example</a> </h6> <pre class="programlisting"><span class="keyword">typedef</span> <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="identifier">empty_vec</span><span class="special">;</span> <span class="keyword">typedef</span> <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">float</span><span class="special">,</span><span class="keyword">char</span><span class="special">></span> <span class="identifier">vec</span><span class="special">;</span> <span class="identifier">BOOST_MPL_ASSERT</span><span class="special">((</span><a class="link" href="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">empty_vec</span><span class="special">>));</span> <span class="identifier">BOOST_MPL_ASSERT_NOT</span><span class="special">((</span><a class="link" href="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">vec</span><span class="special">>));</span> </pre> </div> <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> <td align="left"></td> <td align="right"><div class="copyright-footer">Copyright © 2001-2007 Joel de Guzman, Dan Marsden, Tobias Schwinger<p> Distributed under the Boost Software License, Version 1.0. (See accompanying 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>) </p> </div></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="end.html"><img src="../../../../../../../../doc/html/images/prev.png" alt="Prev"></a><a accesskey="u" href="../metafunctions.html"><img src="../../../../../../../../doc/html/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/html/images/home.png" alt="Home"></a><a accesskey="n" href="front.html"><img src="../../../../../../../../doc/html/images/next.png" alt="Next"></a> </div> </body> </html>