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

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  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="boost_typetraits.reference.is_final"></a><a class="link" href="is_final.html" title="is_final">is_final</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">is_final</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         class type declared with the final specifier type 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         Currently requires some kind of compiler support.
  37       </p>
  38 <p>
  39         <span class="bold"><strong>C++ Standard Reference:</strong></span> 9p3.
  40       </p>
  41 <p>
  42         <span class="bold"><strong>Compiler Compatibility:</strong></span> Without (some as
  43         yet unspecified) help from the compiler, we cannot detect class types declared
  44         with the final specifier using only standard C++, as a result this type will
  45         never inherit from <a class="link" href="integral_constant.html" title="integral_constant">true_type</a>,
  46         unless the user explicitly specializes the template for their user-defined
  47         final class types, or unless the compiler supplies some unspecified intrinsic
  48         that implements this functionality. Currently (June 2015) compilers more
  49         recent than GCC-4.7, Oracle-12.4, and Clang have the necessary compiler
  50         <a class="link" href="../intrinsics.html" title="Support for Compiler Intrinsics">intrinsics</a> to ensure that
  51         this trait "just works". You may also test to see if the necessary
  52         <a class="link" href="../intrinsics.html" title="Support for Compiler Intrinsics">intrinsics</a> are available
  53         by checking to see if the macro <code class="computeroutput"><span class="identifier">BOOST_IS_FINAL</span></code>
  54         is defined.
  55       </p>
  56 <p>
  57         <span class="bold"><strong>Header:</strong></span> <code class="computeroutput"> <span class="preprocessor">#include</span>
  58         <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">is_final</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
  59         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>
  60       </p>
  61 <p>
  62         <span class="bold"><strong>Examples:</strong></span>
  63       </p>
  64 <p>
  65         Given <code class="computeroutput"><span class="keyword">struct</span> <span class="identifier">my_final</span>
  66         <span class="identifier">final</span> <span class="special">{};</span></code>
  67         then:
  68       </p>
  69 <div class="blockquote"><blockquote class="blockquote"><p>
  70           <code class="computeroutput"><span class="identifier">is_final</span><span class="special">&lt;</span><span class="identifier">my_final</span><span class="special">&gt;</span></code>
  71           inherits from <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">true_type</a></code>.
  72         </p></blockquote></div>
  73 <div class="blockquote"><blockquote class="blockquote"><p>
  74           <code class="computeroutput"><span class="identifier">is_final</span><span class="special">&lt;</span><span class="keyword">const</span> <span class="identifier">my_final</span><span class="special">&gt;::</span><span class="identifier">type</span></code>
  75           is the type <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">true_type</a></code>.
  76         </p></blockquote></div>
  77 <div class="blockquote"><blockquote class="blockquote"><p>
  78           <code class="computeroutput"><span class="identifier">is_final</span><span class="special">&lt;</span><span class="identifier">my_final</span><span class="special">&gt;::</span><span class="identifier">value</span></code> is an integral constant expression
  79           that evaluates to <span class="emphasis"><em>true</em></span>.
  80         </p></blockquote></div>
  81 <div class="blockquote"><blockquote class="blockquote"><p>
  82           <code class="computeroutput"><span class="identifier">is_final</span><span class="special">&lt;</span><span class="identifier">my_final</span><span class="special">*&gt;::</span><span class="identifier">value</span></code> is an integral constant expression
  83           that evaluates to <span class="emphasis"><em>false</em></span>.
  84         </p></blockquote></div>
  85 <div class="blockquote"><blockquote class="blockquote"><p>
  86           <code class="computeroutput"><span class="identifier">is_final</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">value_type</span></code> is the type <code class="computeroutput"><span class="keyword">bool</span></code>.
  87         </p></blockquote></div>
  88 </div>
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  91 <td align="right"><div class="copyright-footer">Copyright &#169; 2000, 2011 Adobe Systems Inc, David Abrahams,
  92       Frederic Bron, Steve Cleary, Beman Dawes, Aleksey Gurtovoy, Howard Hinnant,
  93       Jesse Jones, Mat Marcus, Itay Maman, John Maddock, Alexander Nasonov, Thorsten
  94       Ottosen, Roman Perepelitsa, Robert Ramey, Jeremy Siek, Robert Stewart and Steven
  95       Watanabe<p>
  96         Distributed under the Boost Software License, Version 1.0. (See accompanying
  97         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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