<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>has_trivial_assign</title> <link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.74.0"> <link rel="home" href="../../index.html" title="Chapter 1. Boost.TypeTraits"> <link rel="up" href="../reference.html" title="Alphabetical Reference"> <link rel="prev" href="has_no_throw_def_cons.html" title="has_nothrow_default_constructor"> <link rel="next" href="has_trivial_constructor.html" title="has_trivial_constructor"> </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="../../../../../../libs/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="has_no_throw_def_cons.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="has_trivial_constructor.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> </div> <div class="section" lang="en"> <div class="titlepage"><div><div><h3 class="title"> <a name="boost_typetraits.reference.has_trivial_assign"></a><a class="link" href="has_trivial_assign.html" title="has_trivial_assign"> has_trivial_assign</a> </h3></div></div></div> <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="keyword">struct</span> <span class="identifier">has_trivial_assign</span> <span class="special">:</span> <span class="keyword">public</span> <em class="replaceable"><code><a class="link" href="integral_constant.html" title="integral_constant">true_type</a>-or-<a class="link" href="integral_constant.html" title="integral_constant">false_type</a></code></em> <span class="special">{};</span> </pre> <p> <span class="bold"><strong>Inherits:</strong></span> If T is a (possibly cv-qualified) type with a trivial assignment-operator then inherits from <a class="link" href="integral_constant.html" title="integral_constant">true_type</a>, otherwise inherits from <a class="link" href="integral_constant.html" title="integral_constant">false_type</a>. </p> <p> If a type has a trivial assignment-operator then the operator has the same effect as copying the bits of one object to the other: calls to the operator can be safely replaced with a call to <code class="computeroutput"><span class="identifier">memcpy</span></code>. </p> <p> <span class="bold"><strong>Compiler Compatibility:</strong></span> If the compiler does not support partial-specialization of class templates, then this template can not be used with function types. </p> <p> Without some (as yet unspecified) help from the compiler, has_trivial_assign will never report that a user-defined class or struct has a trivial constructor; this is always safe, if possibly sub-optimal. Currently (May 2005) only MWCW 9 and Visual C++ 8 have the necessary compiler <a class="link" href="../intrinsics.html" title="Support for Compiler Intrinsics">intrinsics</a> to detect user-defined classes with trivial constructors. </p> <p> <span class="bold"><strong>C++ Standard Reference:</strong></span> 12.8p11. </p> <p> <span class="bold"><strong>Header:</strong></span> <code class="computeroutput"> <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">/</span><span class="identifier">has_trivial_assign</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code> or <code class="computeroutput"> <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span></code> </p> <p> <span class="bold"><strong>Examples:</strong></span> </p> <div class="blockquote"><blockquote class="blockquote"><p> <code class="computeroutput"><span class="identifier">has_trivial_assign</span><span class="special"><</span><span class="keyword">int</span><span class="special">></span></code> inherits from <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">true_type</a></code>. </p></blockquote></div> <div class="blockquote"><blockquote class="blockquote"><p> <code class="computeroutput"><span class="identifier">has_trivial_assign</span><span class="special"><</span><span class="keyword">char</span><span class="special">*>::</span><span class="identifier">type</span></code> is the type <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">true_type</a></code>. </p></blockquote></div> <div class="blockquote"><blockquote class="blockquote"><p> <code class="computeroutput"><span class="identifier">has_trivial_assign</span><span class="special"><</span><span class="keyword">int</span> <span class="special">(*)(</span><span class="keyword">long</span><span class="special">)>::</span><span class="identifier">value</span></code> is an integral constant expression that evaluates to <span class="emphasis"><em>true</em></span>. </p></blockquote></div> <div class="blockquote"><blockquote class="blockquote"><p> <code class="computeroutput"><span class="identifier">has_trivial_assign</span><span class="special"><</span><span class="identifier">MyClass</span><span class="special">>::</span><span class="identifier">value</span></code> is an integral constant expression that evaluates to <span class="emphasis"><em>false</em></span>. </p></blockquote></div> <div class="blockquote"><blockquote class="blockquote"><p> <code class="computeroutput"><span class="identifier">has_trivial_assign</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value_type</span></code> is the type <code class="computeroutput"><span class="keyword">bool</span></code>. </p></blockquote></div> </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 © 2000, 2006 Adobe Systems Inc, David Abrahams, Steve Cleary, Beman Dawes, Aleksey Gurtovoy, Howard Hinnant, Jesse Jones, Mat Marcus, Itay Maman, John Maddock, Alexander Nasonov, Thorsten Ottosen, Robert Ramey and Jeremy Siek<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="has_no_throw_def_cons.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="has_trivial_constructor.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> </div> </body> </html>