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

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  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="boost_typetraits.reference.is_abstract"></a><a class="link" href="is_abstract.html" title="is_abstract">is_abstract</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_abstract</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         abstract 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       </p>
  37 <p>
  38         <span class="bold"><strong>C++ Standard Reference:</strong></span> 10.3.
  39       </p>
  40 <p>
  41         <span class="bold"><strong>Header:</strong></span> <code class="computeroutput"> <span class="preprocessor">#include</span>
  42         <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_abstract</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
  43         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>
  44       </p>
  45 <p>
  46         <span class="bold"><strong>Compiler Compatibility:</strong></span> The compiler must
  47         support DR337 (as of April 2005: GCC 3.4, VC++ 7.1 (and later), Intel C++
  48         7 (and later), and Comeau 4.3.2). Otherwise behaves the same as <a class="link" href="is_polymorphic.html" title="is_polymorphic">is_polymorphic</a>;
  49         this is the "safe fallback position" for which polymorphic types
  50         are always regarded as potentially abstract. The macro BOOST_NO_IS_ABSTRACT
  51         is used to signify that the implementation is buggy, users should check for
  52         this in their own code if the "safe fallback" is not suitable for
  53         their particular use-case.
  54       </p>
  55 <p>
  56         <span class="bold"><strong>Examples:</strong></span>
  57       </p>
  58 <div class="blockquote"><blockquote class="blockquote"><p>
  59           Given: <code class="computeroutput"><span class="keyword">class</span> <span class="identifier">abc</span><span class="special">{</span> <span class="keyword">virtual</span> <span class="special">~</span><span class="identifier">abc</span><span class="special">()</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="special">};</span></code>
  60         </p></blockquote></div>
  61 <div class="blockquote"><blockquote class="blockquote"><p>
  62           <code class="computeroutput"><span class="identifier">is_abstract</span><span class="special">&lt;</span><span class="identifier">abc</span><span class="special">&gt;</span></code>
  63           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">is_abstract</span><span class="special">&lt;</span><span class="identifier">abc</span><span class="special">&gt;::</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>.
  67         </p></blockquote></div>
  68 <div class="blockquote"><blockquote class="blockquote"><p>
  69           <code class="computeroutput"><span class="identifier">is_abstract</span><span class="special">&lt;</span><span class="identifier">abc</span> <span class="keyword">const</span><span class="special">&gt;::</span><span class="identifier">value</span></code>
  70           is an integral constant expression that evaluates to <span class="emphasis"><em>true</em></span>.
  71         </p></blockquote></div>
  72 <div class="blockquote"><blockquote class="blockquote"><p>
  73           <code class="computeroutput"><span class="identifier">is_abstract</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>.
  74         </p></blockquote></div>
  75 </div>
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