1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>integral_constant</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. Boost.TypeTraits"> 8<link rel="up" href="../reference.html" title="Alphabetical Reference"> 9<link rel="prev" href="has_virtual_destructor.html" title="has_virtual_destructor"> 10<link rel="next" href="integral_promotion.html" title="integral_promotion"> 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="has_virtual_destructor.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.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="integral_promotion.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h3 class="title"> 27<a name="boost_typetraits.reference.integral_constant"></a><a class="link" href="integral_constant.html" title="integral_constant">integral_constant</a> 28</h3></div></div></div> 29<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">,</span> <span class="identifier">T</span> <span class="identifier">val</span><span class="special">></span> 30<span class="keyword">struct</span> <span class="identifier">integral_constant</span> 31<span class="special">{</span> 32 <span class="keyword">typedef</span> <span class="identifier">integral_constant</span><span class="special"><</span><span class="identifier">T</span><span class="special">,</span> <span class="identifier">val</span><span class="special">></span> <span class="identifier">type</span><span class="special">;</span> 33 <span class="keyword">typedef</span> <span class="identifier">T</span> <span class="identifier">value_type</span><span class="special">;</span> 34 <span class="keyword">static</span> <span class="keyword">const</span> <span class="identifier">T</span> <span class="identifier">value</span> <span class="special">=</span> <span class="identifier">val</span><span class="special">;</span> 35 <span class="keyword">constexpr</span> <span class="keyword">operator</span> <span class="identifier">T</span><span class="special">()</span><span class="keyword">const</span><span class="special">;</span> 36<span class="special">};</span> 37 38<span class="keyword">typedef</span> <span class="identifier">integral_constant</span><span class="special"><</span><span class="keyword">bool</span><span class="special">,</span> <span class="keyword">true</span><span class="special">></span> <span class="identifier">true_type</span><span class="special">;</span> 39<span class="keyword">typedef</span> <span class="identifier">integral_constant</span><span class="special"><</span><span class="keyword">bool</span><span class="special">,</span> <span class="keyword">false</span><span class="special">></span> <span class="identifier">false_type</span><span class="special">;</span> 40</pre> 41<p> 42 Class template <code class="computeroutput"><span class="identifier">integral_constant</span></code> 43 is the common base class for all the value-based type traits. The two typedef's 44 <code class="computeroutput"><span class="identifier">true_type</span></code> and <code class="computeroutput"><span class="identifier">false_type</span></code> are provided for convenience: 45 most of the value traits are Boolean properties and so will inherit from 46 one of these. 47 </p> 48</div> 49<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 50<td align="left"></td> 51<td align="right"><div class="copyright-footer">Copyright © 2000, 2011 Adobe Systems Inc, David Abrahams, 52 Frederic Bron, Steve Cleary, Beman Dawes, Glen Fernandes, Aleksey Gurtovoy, 53 Howard Hinnant, Jesse Jones, Mat Marcus, Itay Maman, John Maddock, Alexander 54 Nasonov, Thorsten Ottosen, Roman Perepelitsa, Robert Ramey, Jeremy Siek, Robert 55 Stewart and Steven Watanabe<p> 56 Distributed under the Boost Software License, Version 1.0. (See accompanying 57 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>) 58 </p> 59</div></td> 60</tr></table> 61<hr> 62<div class="spirit-nav"> 63<a accesskey="p" href="has_virtual_destructor.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.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="integral_promotion.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 64</div> 65</body> 66</html> 67
