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  26 <div class="refentry">
  27 <a name="boost.intrusive.pointer_traits"></a><div class="titlepage"></div>
  28 <div class="refnamediv">
  29 <h2><span class="refentrytitle">Struct template pointer_traits</span></h2>
  30 <p>boost::intrusive::pointer_traits</p>
  31 </div>
  32 <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
  33 <div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="../../intrusive/reference.html#header.boost.intrusive.pointer_traits_hpp" title="Header &lt;boost/intrusive/pointer_traits.hpp&gt;">boost/intrusive/pointer_traits.hpp</a>&gt;
  34
  35 </span><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Ptr<span class="special">&gt;</span>
  36 <span class="keyword">struct</span> <a class="link" href="pointer_traits.html" title="Struct template pointer_traits">pointer_traits</a> <span class="special">{</span>
  37   <span class="comment">// <a class="link" href="pointer_traits.html#boost.intrusive.pointer_traitstypes">types</a></span>
  38   <span class="keyword">typedef</span> <span class="identifier">Ptr</span>              <a class="link" href="pointer_traits.html#boost.intrusive.pointer_traits.pointer"><span class="identifier">pointer</span></a><span class="special">;</span>
  39   <span class="keyword">typedef</span> <span class="identifier">unspecified_type</span> <a class="link" href="pointer_traits.html#boost.intrusive.pointer_traits.element_type"><span class="identifier">element_type</span></a><span class="special">;</span>
  40   <span class="keyword">typedef</span> <span class="identifier">unspecified_type</span> <a class="link" href="pointer_traits.html#boost.intrusive.pointer_traits.difference_type"><span class="identifier">difference_type</span></a><span class="special">;</span>
  41   <span class="keyword">typedef</span> <span class="identifier">unspecified</span>      <a class="link" href="pointer_traits.html#boost.intrusive.pointer_traits.rebind"><span class="identifier">rebind</span></a><span class="special">;</span>
  42   <span class="keyword">typedef</span> <span class="identifier">unspecified_type</span> <a class="link" href="pointer_traits.html#boost.intrusive.pointer_traits.reference"><span class="identifier">reference</span></a><span class="special">;</span>
  43
  44   <span class="comment">// <a class="link" href="pointer_traits.html#idm45581297717568-bb">public static functions</a></span>
  45   <span class="keyword">static</span> <span class="identifier">pointer</span> <a class="link" href="pointer_traits.html#idm45581297717008-bb"><span class="identifier">pointer_to</span></a><span class="special">(</span><span class="identifier">reference</span><span class="special">)</span><span class="special">;</span>
  46   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> UPtr<span class="special">&gt;</span> <span class="keyword">static</span> <span class="identifier">pointer</span> <a class="link" href="pointer_traits.html#idm45581297711760-bb"><span class="identifier">static_cast_from</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">UPtr</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  47   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> UPtr<span class="special">&gt;</span> <span class="keyword">static</span> <span class="identifier">pointer</span> <a class="link" href="pointer_traits.html#idm45581297705712-bb"><span class="identifier">const_cast_from</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">UPtr</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  48   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> UPtr<span class="special">&gt;</span> <span class="keyword">static</span> <span class="identifier">pointer</span> <a class="link" href="pointer_traits.html#idm45581297699664-bb"><span class="identifier">dynamic_cast_from</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">UPtr</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  49 <span class="special">}</span><span class="special">;</span></pre></div>
  50 <div class="refsect1">
  51 <a name="id-1.3.20.42.26.3.4"></a><h2>Description</h2>
  52 <p><a class="link" href="pointer_traits.html" title="Struct template pointer_traits">pointer_traits</a> is the implementation of C++11 std::pointer_traits class with some extensions like castings.</p>
  53 <p><a class="link" href="pointer_traits.html" title="Struct template pointer_traits">pointer_traits</a> supplies a uniform interface to certain attributes of pointer-like types.</p>
  54 <p><span class="bold"><strong>Note</strong></span>: When defining a custom family of pointers or references to be used with BI library, make sure the public static conversion functions accessed through the <code class="computeroutput"><a class="link" href="pointer_traits.html" title="Struct template pointer_traits">pointer_traits</a></code> interface (<code class="computeroutput">*_cast_from</code> and <code class="computeroutput">pointer_to</code>) can properly convert between const and nonconst referred member types <span class="bold"><strong>without the use of implicit constructor calls</strong></span>. It is suggested these conversions be implemented as function templates, where the template argument is the type of the object being converted from. </p>
  55 <div class="refsect2">
  56 <a name="id-1.3.20.42.26.3.4.5"></a><h3>
  57 <a name="boost.intrusive.pointer_traitstypes"></a><code class="computeroutput">pointer_traits</code>
  58         public
  59        types</h3>
  60 <div class="orderedlist"><ol class="orderedlist" type="1">
  61 <li class="listitem">
  62 <p>
  63 <span class="keyword">typedef</span> <span class="identifier">Ptr</span> <a name="boost.intrusive.pointer_traits.pointer"></a><span class="identifier">pointer</span><span class="special">;</span></p>
  64 <p>The pointer type queried by this <a class="link" href="pointer_traits.html" title="Struct template pointer_traits">pointer_traits</a> instantiation </p>
  65 </li>
  66 <li class="listitem">
  67 <p>
  68 <span class="keyword">typedef</span> <span class="identifier">unspecified_type</span> <a name="boost.intrusive.pointer_traits.element_type"></a><span class="identifier">element_type</span><span class="special">;</span></p>
  69 <p>Ptr::element_type if such a type exists; otherwise, T if Ptr is a class template instantiation of the form SomePointer&lt;T, Args&gt;, where Args is zero or more type arguments ; otherwise , the specialization is ill-formed. </p>
  70 </li>
  71 <li class="listitem">
  72 <p>
  73 <span class="keyword">typedef</span> <span class="identifier">unspecified_type</span> <a name="boost.intrusive.pointer_traits.difference_type"></a><span class="identifier">difference_type</span><span class="special">;</span></p>
  74 <p>Ptr::difference_type if such a type exists; otherwise, std::ptrdiff_t. </p>
  75 </li>
  76 <li class="listitem">
  77 <p>
  78 <span class="keyword">typedef</span> <span class="identifier">unspecified</span> <a name="boost.intrusive.pointer_traits.rebind"></a><span class="identifier">rebind</span><span class="special">;</span></p>
  79 <p>Ptr::rebind&lt;U&gt; if such a type exists; otherwise, SomePointer&lt;U, Args&gt; if Ptr is a class template instantiation of the form SomePointer&lt;T, Args&gt;, where Args is zero or more type arguments ; otherwise, the instantiation of rebind is ill-formed.</p>
  80 <p>For portable code for C++03 and C++11, </p>
  81 <pre class="programlisting"><span class="keyword">typename</span> <span class="identifier">rebind_pointer</span><span class="special">&lt;</span><span class="identifier">U</span><span class="special">&gt;</span><span class="special">::</span><span class="identifier">type</span></pre>
  82 <p> shall be used instead of rebind<span style="color: red">&lt;underline&gt; to obtain a pointer to U. &lt;/underline&gt;</span></p>
  83 </li>
  84 <li class="listitem">
  85 <p>
  86 <span class="keyword">typedef</span> <span class="identifier">unspecified_type</span> <a name="boost.intrusive.pointer_traits.reference"></a><span class="identifier">reference</span><span class="special">;</span></p>
  87 <p>Ptr::reference if such a type exists (non-standard extension); otherwise, element_type &amp; </p>
  88 </li>
  89 </ol></div>
  90 </div>
  91 <div class="refsect2">
  92 <a name="id-1.3.20.42.26.3.4.6"></a><h3>
  93 <a name="idm45581297717568-bb"></a><code class="computeroutput">pointer_traits</code> public static functions</h3>
  94 <div class="orderedlist"><ol class="orderedlist" type="1">
  95 <li class="listitem">
  96 <pre class="literallayout"><span class="keyword">static</span> <span class="identifier">pointer</span> <a name="idm45581297717008-bb"></a><span class="identifier">pointer_to</span><span class="special">(</span><span class="identifier">reference</span> r<span class="special">)</span><span class="special">;</span></pre>
  97 <p><span class="bold"><strong>Remark</strong></span>: If element_type is (possibly cv-qualified) void, r type is unspecified; otherwise, it is element_type &amp;.</p>
  98 <p><span class="bold"><strong>Returns</strong></span>: A dereferenceable pointer to r obtained by calling Ptr::pointer_to(reference). Non-standard extension: If such function does not exist, returns pointer(addressof(r));</p>
  99 <p><span class="bold"><strong>Note</strong></span>: For non-conforming compilers only the existence of a member function called <code class="computeroutput">pointer_to</code> is checked. </p>
 100 </li>
 101 <li class="listitem">
 102 <pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> UPtr<span class="special">&gt;</span> <span class="keyword">static</span> <span class="identifier">pointer</span> <a name="idm45581297711760-bb"></a><span class="identifier">static_cast_from</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">UPtr</span> <span class="special">&amp;</span> uptr<span class="special">)</span><span class="special">;</span></pre>
 103 <p><span class="bold"><strong>Remark</strong></span>: Non-standard extension.</p>
 104 <p><span class="bold"><strong>Returns</strong></span>: A dereferenceable pointer to r obtained by calling the static template function Ptr::static_cast_from(UPpr/const UPpr &amp;). If such function does not exist, returns pointer_to(static_cast&lt;element_type&amp;&gt;(*uptr))</p>
 105 <p><span class="bold"><strong>Note</strong></span>: For non-conforming compilers only the existence of a member function called <code class="computeroutput">static_cast_from</code> is checked. </p>
 106 </li>
 107 <li class="listitem">
 108 <pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> UPtr<span class="special">&gt;</span> <span class="keyword">static</span> <span class="identifier">pointer</span> <a name="idm45581297705712-bb"></a><span class="identifier">const_cast_from</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">UPtr</span> <span class="special">&amp;</span> uptr<span class="special">)</span><span class="special">;</span></pre>
 109 <p><span class="bold"><strong>Remark</strong></span>: Non-standard extension.</p>
 110 <p><span class="bold"><strong>Returns</strong></span>: A dereferenceable pointer to r obtained by calling the static template function Ptr::const_cast_from&lt;UPtr&gt;(UPpr/const UPpr &amp;). If such function does not exist, returns pointer_to(const_cast&lt;element_type&amp;&gt;(*uptr))</p>
 111 <p><span class="bold"><strong>Note</strong></span>: For non-conforming compilers only the existence of a member function called <code class="computeroutput">const_cast_from</code> is checked. </p>
 112 </li>
 113 <li class="listitem">
 114 <pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> UPtr<span class="special">&gt;</span> <span class="keyword">static</span> <span class="identifier">pointer</span> <a name="idm45581297699664-bb"></a><span class="identifier">dynamic_cast_from</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">UPtr</span> <span class="special">&amp;</span> uptr<span class="special">)</span><span class="special">;</span></pre>
 115 <p><span class="bold"><strong>Remark</strong></span>: Non-standard extension.</p>
 116 <p><span class="bold"><strong>Returns</strong></span>: A dereferenceable pointer to r obtained by calling the static template function Ptr::dynamic_cast_from&lt;UPtr&gt;(UPpr/const UPpr &amp;). If such function does not exist, returns pointer_to(<span class="emphasis"><em>dynamic_cast&lt;element_type</em></span>&gt;(&amp;*uptr))</p>
 117 <p><span class="bold"><strong>Note</strong></span>: For non-conforming compilers only the existence of a member function called <code class="computeroutput">dynamic_cast_from</code> is checked. </p>
 118 </li>
 119 </ol></div>
 120 </div>
 121 </div>
 122 </div>
 123 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 124 <td align="left"></td>
 125 <td align="right"><div class="copyright-footer">Copyright &#169; 2005 Olaf Krzikalla<br>Copyright &#169; 2006-2015 Ion Gaztanaga<p>
 126         Distributed under the Boost Software License, Version 1.0. (See accompanying
 127         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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