ceph/src/boost/libs/type_traits/doc/html/boost_typetraits/reference/has_trivial_move_assign.html

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  27 <a name="boost_typetraits.reference.has_trivial_move_assign"></a><a class="link" href="has_trivial_move_assign.html" title="has_trivial_move_assign">has_trivial_move_assign</a>
  28 </h3></div></div></div>
  29 <pre class="programlisting"><span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">&gt;</span>
  30 <span class="keyword">struct</span> <span class="identifier">has_trivial_move_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>
  31 </pre>
  32 <p>
  33         <span class="bold"><strong>Inherits:</strong></span> If T is a (possibly cv-qualified)
  34         type with a trivial move assignment-operator then inherits from <a class="link" href="integral_constant.html" title="integral_constant">true_type</a>,
  35         otherwise inherits from <a class="link" href="integral_constant.html" title="integral_constant">false_type</a>.
  36       </p>
  37 <p>
  38         If a type has a trivial move assignment-operator then the operator has the
  39         same effect as copying the bits of one object to the other: calls to the
  40         operator can be safely replaced with a call to <code class="computeroutput"><span class="identifier">memcpy</span></code>.
  41       </p>
  42 <p>
  43         <span class="bold"><strong>Compiler Compatibility:</strong></span> Without some (as
  44         yet unspecified) help from the compiler, has_trivial_move_assign will never
  45         report that a user-defined class or struct has a trivial move assign; this
  46         is always safe, if possibly sub-optimal. In addition, in order to correctly
  47         handle private or deleted move assignment operators then c++11's <code class="computeroutput"><span class="keyword">decltype</span></code> is required. Currently (June 2015)
  48         compilers that have the necessary <a class="link" href="../intrinsics.html" title="Support for Compiler Intrinsics">intrinsics</a>
  49         to ensure that this trait "just works" include Clang, GCC-5.1 and
  50         MSVC-12.0. You may also test to see if the necessary <a class="link" href="../intrinsics.html" title="Support for Compiler Intrinsics">intrinsics</a>
  51         are available by checking to see if the macro <code class="computeroutput"><span class="identifier">BOOST_HAS_TRIVIAL_MOVE_ASSIGN</span></code>
  52         is defined.
  53       </p>
  54 <p>
  55         <span class="bold"><strong>Header:</strong></span> <code class="computeroutput"> <span class="preprocessor">#include</span>
  56         <span class="special">&lt;</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_move_assign</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
  57         or <code class="computeroutput"> <span class="preprocessor">#include</span> <span class="special">&lt;</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">&gt;</span></code>
  58       </p>
  59 <p>
  60         <span class="bold"><strong>Examples:</strong></span>
  61       </p>
  62 <div class="blockquote"><blockquote class="blockquote"><p>
  63           <code class="computeroutput"><span class="identifier">has_trivial_move_assign</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span></code> inherits from <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">true_type</a></code>.
  64         </p></blockquote></div>
  65 <div class="blockquote"><blockquote class="blockquote"><p>
  66           <code class="computeroutput"><span class="identifier">has_trivial_move_assign</span><span class="special">&lt;</span><span class="keyword">char</span><span class="special">*&gt;::</span><span class="identifier">type</span></code>
  67           is the type <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">true_type</a></code>.
  68         </p></blockquote></div>
  69 <div class="blockquote"><blockquote class="blockquote"><p>
  70           <code class="computeroutput"><span class="identifier">has_trivial_move_assign</span><span class="special">&lt;</span><span class="keyword">int</span> <span class="special">(*)(</span><span class="keyword">long</span><span class="special">)&gt;::</span><span class="identifier">value</span></code>
  71           is an integral constant expression that evaluates to <span class="emphasis"><em>true</em></span>.
  72         </p></blockquote></div>
  73 <div class="blockquote"><blockquote class="blockquote"><p>
  74           <code class="computeroutput"><span class="identifier">has_trivial_move_assign</span><span class="special">&lt;</span><span class="identifier">MyClass</span><span class="special">&gt;::</span><span class="identifier">value</span></code>
  75           is an integral constant expression that evaluates to <span class="emphasis"><em>false</em></span>.
  76         </p></blockquote></div>
  77 <div class="blockquote"><blockquote class="blockquote"><p>
  78           <code class="computeroutput"><span class="identifier">has_trivial_move_assign</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">value_type</span></code>
  79           is the type <code class="computeroutput"><span class="keyword">bool</span></code>.
  80         </p></blockquote></div>
  81 </div>
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  84 <td align="right"><div class="copyright-footer">Copyright &#169; 2000, 2011 Adobe Systems Inc, David Abrahams,
  85       Frederic Bron, Steve Cleary, Beman Dawes, Aleksey Gurtovoy, Howard Hinnant,
  86       Jesse Jones, Mat Marcus, Itay Maman, John Maddock, Alexander Nasonov, Thorsten
  87       Ottosen, Roman Perepelitsa, Robert Ramey, Jeremy Siek, Robert Stewart and Steven
  88       Watanabe<p>
  89         Distributed under the Boost Software License, Version 1.0. (See accompanying
  90         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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