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<title>is_stateless</title>
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<div class="section boost_typetraits_reference_is_stateless">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_typetraits.reference.is_stateless"></a><a class="link" href="is_stateless.html" title="is_stateless">is_stateless</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">is_stateless</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 stateless type then
inherits from <a class="link" href="integral_constant.html" title="integral_constant">true_type</a>,
otherwise from <a class="link" href="integral_constant.html" title="integral_constant">false_type</a>.
</p>
<p>
Type T must be a complete type.
</p>
<p>
A stateless type is a type that has no storage and whose constructors and
destructors are trivial. That means that <code class="computeroutput"><span class="identifier">is_stateless</span></code>
only inherits from <a class="link" href="integral_constant.html" title="integral_constant">true_type</a>
if the following expression is <code class="computeroutput"><span class="keyword">true</span></code>:
</p>
<pre class="programlisting"><span class="special">::</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">has_trivial_constructor</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span>
<span class="special">&&</span> <span class="special">::</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">has_trivial_copy</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span>
<span class="special">&&</span> <span class="special">::</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">has_trivial_destructor</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span>
<span class="special">&&</span> <span class="special">::</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_class</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span>
<span class="special">&&</span> <span class="special">::</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_empty</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span>
</pre>
<p>
<span class="bold"><strong>C++ Standard Reference:</strong></span> 3.9p10.
</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">is_stateless</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>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, is_stateless will
never report that a class or struct is stateless; this is always safe, if
possibly sub-optimal. Currently (May 2011) compilers more recent than Visual
C++ 8, GCC-4.3, Greenhills 6.0, Intel-11.0, and Codegear have the necessary
compiler <a class="link" href="../intrinsics.html" title="Support for Compiler Intrinsics">intrinsics</a> to
ensure that this trait "just works".
</p>
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<td align="right"><div class="copyright-footer">Copyright © 2000, 2011 Adobe Systems Inc, David Abrahams,
Frederic Bron, Steve Cleary, Beman Dawes, Aleksey Gurtovoy, Howard Hinnant,
Jesse Jones, Mat Marcus, Itay Maman, John Maddock, Alexander Nasonov, Thorsten
Ottosen, Roman Perepelitsa, Robert Ramey, Jeremy Siek, Robert Stewart and Steven
Watanabe<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>)
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