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

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  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="boost_typetraits.reference.is_virtual_base_of"></a><a class="link" href="is_virtual_base_of.html" title="is_virtual_base_of">is_virtual_base_of</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">Base</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Derived</span><span class="special">&gt;</span>
  30 <span class="keyword">struct</span> <span class="identifier">is_virtual_base_of</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 Base is a virtual base class
  34         of type Derived 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         Types <code class="computeroutput"><span class="identifier">Base</span></code> and <code class="computeroutput"><span class="identifier">Derived</span></code> must not be incomplete types.
  39       </p>
  40 <p>
  41         <span class="bold"><strong>C++ Standard Reference:</strong></span> 10.
  42       </p>
  43 <p>
  44         <span class="bold"><strong>Header:</strong></span> <code class="computeroutput"> <span class="preprocessor">#include</span>
  45         <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_virtual_base_of</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
  46         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>
  47       </p>
  48 <p>
  49         <span class="bold"><strong>Compiler Compatibility:</strong></span> All current compilers
  50         are supported by this trait.
  51       </p>
  52 <div class="note"><table border="0" summary="Note">
  53 <tr>
  54 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../doc/src/images/note.png"></td>
  55 <th align="left">Note</th>
  56 </tr>
  57 <tr><td align="left" valign="top"><p>
  58           There are a small number of cases where it's simply not possible for this
  59           trait to work, and where attempting to instantiate the trait will cause
  60           compiler errors (see bug reports <a href="https://svn.boost.org/trac/boost/ticket/3730" target="_top">#3730</a>
  61           and <a href="https://svn.boost.org/trac/boost/ticket/11323" target="_top">11323</a>).
  62           Further more the issues may well be compiler specific. In this situation
  63           the user should supply a full specialization of the trait to work around
  64           the problem.
  65         </p></td></tr>
  66 </table></div>
  67 <p>
  68         <span class="bold"><strong>Examples:</strong></span>
  69       </p>
  70 <div class="blockquote"><blockquote class="blockquote"><p>
  71           Given: <code class="computeroutput"> <span class="keyword">class</span> <span class="identifier">Base</span><span class="special">{};</span> <span class="keyword">class</span> <span class="identifier">Derived</span> <span class="special">:</span> <span class="keyword">public</span> <span class="keyword">virtual</span>
  72           <span class="identifier">Base</span><span class="special">{};</span></code>
  73         </p></blockquote></div>
  74 <div class="blockquote"><blockquote class="blockquote"><p>
  75           <code class="computeroutput"><span class="identifier">is_virtual_base_of</span><span class="special">&lt;</span><span class="identifier">Base</span><span class="special">,</span> <span class="identifier">Derived</span><span class="special">&gt;</span></code>
  76           inherits from <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">true_type</a></code>.
  77         </p></blockquote></div>
  78 <div class="blockquote"><blockquote class="blockquote"><p>
  79           <code class="computeroutput"><span class="identifier">is_virtual_base_of</span><span class="special">&lt;</span><span class="identifier">Base</span><span class="special">,</span> <span class="identifier">Derived</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>.
  80         </p></blockquote></div>
  81 <div class="blockquote"><blockquote class="blockquote"><p>
  82           <code class="computeroutput"><span class="identifier">is_virtual_base_of</span><span class="special">&lt;</span><span class="identifier">Base</span><span class="special">,</span> <span class="identifier">Derived</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>true</em></span>.
  84         </p></blockquote></div>
  85 <div class="blockquote"><blockquote class="blockquote"><p>
  86           <code class="computeroutput"><span class="identifier">is_virtual_base_of</span><span class="special">&lt;</span><span class="identifier">SomeClassType</span><span class="special">,</span>
  87           <span class="identifier">SomeClassType</span><span class="special">&gt;::</span><span class="identifier">value</span></code> is an integral constant expression
  88           that evaluates to <span class="emphasis"><em>true</em></span>.
  89         </p></blockquote></div>
  90 <div class="blockquote"><blockquote class="blockquote"><p>
  91           <code class="computeroutput"><span class="identifier">is_virtual_base_of</span><span class="special">&lt;</span><span class="identifier">NotAClassType</span><span class="special">,</span>
  92           <span class="identifier">NotAClassType</span><span class="special">&gt;::</span><span class="identifier">value</span></code> is an integral constant expression
  93           that evaluates to <span class="emphasis"><em>false</em></span>.
  94         </p></blockquote></div>
  95 <div class="blockquote"><blockquote class="blockquote"><p>
  96           <code class="computeroutput"><span class="identifier">is_virtual_base_of</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">,</span> <span class="identifier">U</span><span class="special">&gt;::</span><span class="identifier">value_type</span></code>
  97           is the type <code class="computeroutput"><span class="keyword">bool</span></code>.
  98         </p></blockquote></div>
  99 </div>
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