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

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  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="boost_typetraits.reference.is_pointer"></a><a class="link" href="is_pointer.html" title="is_pointer">is_pointer</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_pointer</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         pointer type (includes function pointers, but excludes pointers to members)
  35         then inherits from <a class="link" href="integral_constant.html" title="integral_constant">true_type</a>,
  36         otherwise inherits from <a class="link" href="integral_constant.html" title="integral_constant">false_type</a>.
  37       </p>
  38 <p>
  39         <span class="bold"><strong>C++ Standard Reference:</strong></span> 3.9.2p2 and 8.3.1.
  40       </p>
  41 <p>
  42         <span class="bold"><strong>Header:</strong></span> <code class="computeroutput"> <span class="preprocessor">#include</span>
  43         <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_pointer</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
  44         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>
  45       </p>
  46 <p>
  47         <span class="bold"><strong>Compiler Compatibility:</strong></span> All current compilers
  48         are supported by this trait.
  49       </p>
  50 <p>
  51         <span class="bold"><strong>Examples:</strong></span>
  52       </p>
  53 <div class="blockquote"><blockquote class="blockquote"><p>
  54           <code class="computeroutput"><span class="identifier">is_pointer</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">*&gt;</span></code>
  55           inherits from <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">true_type</a></code>.
  56         </p></blockquote></div>
  57 <div class="blockquote"><blockquote class="blockquote"><p>
  58           <code class="computeroutput"><span class="identifier">is_pointer</span><span class="special">&lt;</span><span class="keyword">char</span><span class="special">*</span> <span class="keyword">const</span><span class="special">&gt;::</span><span class="identifier">type</span></code>
  59           is the type <code class="computeroutput"><a class="link" href="integral_constant.html" title="integral_constant">true_type</a></code>.
  60         </p></blockquote></div>
  61 <div class="blockquote"><blockquote class="blockquote"><p>
  62           <code class="computeroutput"><span class="identifier">is_pointer</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> is an integral constant expression
  63           that evaluates to <span class="emphasis"><em>true</em></span>.
  64         </p></blockquote></div>
  65 <div class="blockquote"><blockquote class="blockquote"><p>
  66           <code class="computeroutput"><span class="identifier">is_pointer</span><span class="special">&lt;</span><span class="keyword">int</span> <span class="special">(</span><span class="identifier">MyClass</span><span class="special">::*)(</span><span class="keyword">long</span><span class="special">)&gt;::</span><span class="identifier">value</span></code>
  67           is an integral constant expression that evaluates to <span class="emphasis"><em>false</em></span>.
  68         </p></blockquote></div>
  69 <div class="blockquote"><blockquote class="blockquote"><p>
  70           <code class="computeroutput"><span class="identifier">is_pointer</span><span class="special">&lt;</span><span class="keyword">int</span> <span class="special">(</span><span class="identifier">MyClass</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>false</em></span>.
  72         </p></blockquote></div>
  73 <div class="blockquote"><blockquote class="blockquote"><p>
  74           <code class="computeroutput"><span class="identifier">is_pointer</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>.
  75         </p></blockquote></div>
  76 <div class="important"><table border="0" summary="Important">
  77 <tr>
  78 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Important]" src="../../../../../../doc/src/images/important.png"></td>
  79 <th align="left">Important</th>
  80 </tr>
  81 <tr><td align="left" valign="top"><p>
  82           <code class="computeroutput"><span class="identifier">is_pointer</span></code> detects "real"
  83           pointer types only, and <span class="emphasis"><em>not</em></span> smart pointers. Users
  84           should not specialise <code class="computeroutput"><span class="identifier">is_pointer</span></code>
  85           for smart pointer types, as doing so may cause Boost (and other third party)
  86           code to fail to function correctly. Users wanting a trait to detect smart
  87           pointers should create their own. However, note that there is no way in
  88           general to auto-magically detect smart pointer types, so such a trait would
  89           have to be partially specialised for each supported smart pointer type.
  90         </p></td></tr>
  91 </table></div>
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  94 <td align="left"></td>
  95 <td align="right"><div class="copyright-footer">Copyright &#169; 2000, 2011 Adobe Systems Inc, David Abrahams,
  96       Frederic Bron, Steve Cleary, Beman Dawes, Aleksey Gurtovoy, Howard Hinnant,
  97       Jesse Jones, Mat Marcus, Itay Maman, John Maddock, Alexander Nasonov, Thorsten
  98       Ottosen, Roman Perepelitsa, Robert Ramey, Jeremy Siek, Robert Stewart and Steven
  99       Watanabe<p>
 100         Distributed under the Boost Software License, Version 1.0. (See accompanying
 101         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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