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  25 </div>
  26 <div class="refentry">
  27 <a name="boost.container.pmr.polymorphic_allocator"></a><div class="titlepage"></div>
  28 <div class="refnamediv">
  29 <h2><span class="refentrytitle">Class template polymorphic_allocator</span></h2>
  30 <p>boost::container::pmr::polymorphic_allocator</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="../../../boost_container_header_reference.html#header.boost.container.pmr.polymorphic_allocator_hpp" title="Header &lt;boost/container/pmr/polymorphic_allocator.hpp&gt;">boost/container/pmr/polymorphic_allocator.hpp</a>&gt;
  34
  35 </span><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">&gt;</span>
  36 <span class="keyword">class</span> <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> <span class="special">{</span>
  37 <span class="keyword">public</span><span class="special">:</span>
  38   <span class="comment">// types</span>
  39   <span class="keyword">typedef</span> <span class="identifier">T</span> <a name="boost.container.pmr.polymorphic_allocator.value_type"></a><span class="identifier">value_type</span><span class="special">;</span>
  40
  41   <span class="comment">// <a class="link" href="polymorphic_allocator.html#boost.container.pmr.polymorphic_allocatorconstruct-copy-destruct">construct/copy/destruct</a></span>
  42   <a class="link" href="polymorphic_allocator.html#idp50876512-bb"><span class="identifier">polymorphic_allocator</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
  43   <a class="link" href="polymorphic_allocator.html#idp50878496-bb"><span class="identifier">polymorphic_allocator</span></a><span class="special">(</span><a class="link" href="memory_resource.html" title="Class memory_resource">memory_resource</a> <span class="special">*</span><span class="special">)</span><span class="special">;</span>
  44   <a class="link" href="polymorphic_allocator.html#idp50883424-bb"><span class="identifier">polymorphic_allocator</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  45   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> U<span class="special">&gt;</span>
  46     <a class="link" href="polymorphic_allocator.html#idp50885840-bb"><span class="identifier">polymorphic_allocator</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a><span class="special">&lt;</span> <span class="identifier">U</span> <span class="special">&gt;</span> <span class="special">&amp;</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
  47   <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> <span class="special">&amp;</span> <a class="link" href="polymorphic_allocator.html#idp50889376-bb"><span class="keyword">operator</span><span class="special">=</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  48
  49   <span class="comment">// <a class="link" href="polymorphic_allocator.html#idp50850192-bb">public member functions</a></span>
  50   <span class="identifier">T</span> <span class="special">*</span> <a class="link" href="polymorphic_allocator.html#idp50850752-bb"><span class="identifier">allocate</span></a><span class="special">(</span><span class="identifier">size_t</span><span class="special">)</span><span class="special">;</span>
  51   <span class="keyword">void</span> <a class="link" href="polymorphic_allocator.html#idp50853760-bb"><span class="identifier">deallocate</span></a><span class="special">(</span><span class="identifier">T</span> <span class="special">*</span><span class="special">,</span> <span class="identifier">size_t</span><span class="special">)</span><span class="special">;</span>
  52   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> U<span class="special">,</span> <span class="keyword">class</span><span class="special">...</span> Args<span class="special">&gt;</span> <span class="keyword">void</span> <a class="link" href="polymorphic_allocator.html#idp50859232-bb"><span class="identifier">construct</span></a><span class="special">(</span><span class="identifier">U</span> <span class="special">*</span><span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span><span class="special">...</span><span class="special">)</span><span class="special">;</span>
  53   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> U<span class="special">&gt;</span> <span class="keyword">void</span> <a class="link" href="polymorphic_allocator.html#idp50867920-bb"><span class="identifier">destroy</span></a><span class="special">(</span><span class="identifier">U</span> <span class="special">*</span><span class="special">)</span><span class="special">;</span>
  54   <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> <a class="link" href="polymorphic_allocator.html#idp50871280-bb"><span class="identifier">select_on_container_copy_construction</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  55   <a class="link" href="memory_resource.html" title="Class memory_resource">memory_resource</a> <span class="special">*</span> <a class="link" href="polymorphic_allocator.html#idp50873968-bb"><span class="identifier">resource</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  56 <span class="special">}</span><span class="special">;</span></pre></div>
  57 <div class="refsect1">
  58 <a name="idp192601840"></a><h2>Description</h2>
  59 <p>A specialization of class template <code class="computeroutput"><a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a></code> conforms to the Allocator requirements. Constructed with different memory resources, different instances of the same specialization of <code class="computeroutput"><a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a></code> can exhibit entirely different allocation behavior. This runtime polymorphism allows objects that use <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> to behave as if they used different allocator types at run time even though they use the same static allocator type. </p>
  60 <div class="refsect2">
  61 <a name="idp192606416"></a><h3>
  62 <a name="boost.container.pmr.polymorphic_allocatorconstruct-copy-destruct"></a><code class="computeroutput">polymorphic_allocator</code>
  63         public
  64        construct/copy/destruct</h3>
  65 <div class="orderedlist"><ol class="orderedlist" type="1">
  66 <li class="listitem">
  67 <pre class="literallayout"><a name="idp50876512-bb"></a><span class="identifier">polymorphic_allocator</span><span class="special">(</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></pre>
  68 <p><span class="bold"><strong>Effects</strong></span>: Sets m_resource to <code class="computeroutput">get_default_resource()</code>. </p>
  69 </li>
  70 <li class="listitem">
  71 <pre class="literallayout"><a name="idp50878496-bb"></a><span class="identifier">polymorphic_allocator</span><span class="special">(</span><a class="link" href="memory_resource.html" title="Class memory_resource">memory_resource</a> <span class="special">*</span> r<span class="special">)</span><span class="special">;</span></pre>
  72 <p><span class="bold"><strong>Requires</strong></span>: r is non-null.</p>
  73 <p><span class="bold"><strong>Effects</strong></span>: Sets m_resource to r.</p>
  74 <p><span class="bold"><strong>Throws</strong></span>: Nothing</p>
  75 <p><span class="bold"><strong>Notes</strong></span>: This constructor provides an implicit conversion from memory_resource*. Non-standard extension: if r is null m_resource is set to get_default_resource(). </p>
  76 </li>
  77 <li class="listitem">
  78 <pre class="literallayout"><a name="idp50883424-bb"></a><span class="identifier">polymorphic_allocator</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> <span class="special">&amp;</span> other<span class="special">)</span><span class="special">;</span></pre>
  79 <p><span class="bold"><strong>Effects</strong></span>: Sets m_resource to other.resource(). </p>
  80 </li>
  81 <li class="listitem">
  82 <pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> U<span class="special">&gt;</span>
  83   <a name="idp50885840-bb"></a><span class="identifier">polymorphic_allocator</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a><span class="special">&lt;</span> <span class="identifier">U</span> <span class="special">&gt;</span> <span class="special">&amp;</span> other<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></pre>
  84 <p><span class="bold"><strong>Effects</strong></span>: Sets m_resource to other.resource(). </p>
  85 </li>
  86 <li class="listitem">
  87 <pre class="literallayout"><a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> <span class="special">&amp;</span> <a name="idp50889376-bb"></a><span class="keyword">operator</span><span class="special">=</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> <span class="special">&amp;</span> other<span class="special">)</span><span class="special">;</span></pre>
  88 <p><span class="bold"><strong>Effects</strong></span>: Sets m_resource to other.resource(). </p>
  89 </li>
  90 </ol></div>
  91 </div>
  92 <div class="refsect2">
  93 <a name="idp192650688"></a><h3>
  94 <a name="idp50850192-bb"></a><code class="computeroutput">polymorphic_allocator</code> public member functions</h3>
  95 <div class="orderedlist"><ol class="orderedlist" type="1">
  96 <li class="listitem">
  97 <pre class="literallayout"><span class="identifier">T</span> <span class="special">*</span> <a name="idp50850752-bb"></a><span class="identifier">allocate</span><span class="special">(</span><span class="identifier">size_t</span> n<span class="special">)</span><span class="special">;</span></pre>
  98 <p><span class="bold"><strong>Returns</strong></span>: Equivalent to <code class="computeroutput">static_cast&lt;T*&gt;(m_resource-&gt;allocate(n * sizeof(T), alignof(T)))</code>. </p>
  99 </li>
 100 <li class="listitem">
 101 <pre class="literallayout"><span class="keyword">void</span> <a name="idp50853760-bb"></a><span class="identifier">deallocate</span><span class="special">(</span><span class="identifier">T</span> <span class="special">*</span> p<span class="special">,</span> <span class="identifier">size_t</span> n<span class="special">)</span><span class="special">;</span></pre>
 102 <p><span class="bold"><strong>Requires</strong></span>: p was allocated from a memory resource, x, equal to *m_resource, using <code class="computeroutput">x.allocate(n * sizeof(T), alignof(T))</code>.</p>
 103 <p><span class="bold"><strong>Effects</strong></span>: Equivalent to m_resource-&gt;deallocate(p, n * sizeof(T), alignof(T)).</p>
 104 <p><span class="bold"><strong>Throws</strong></span>: Nothing. </p>
 105 </li>
 106 <li class="listitem">
 107 <pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> U<span class="special">,</span> <span class="keyword">class</span><span class="special">...</span> Args<span class="special">&gt;</span> <span class="keyword">void</span> <a name="idp50859232-bb"></a><span class="identifier">construct</span><span class="special">(</span><span class="identifier">U</span> <span class="special">*</span> p<span class="special">,</span> <span class="identifier">Args</span> <span class="special">&amp;&amp;</span><span class="special">...</span> args<span class="special">)</span><span class="special">;</span></pre>
 108 <p><span class="bold"><strong>Requires</strong></span>: Uses-allocator construction of T with allocator <code class="computeroutput">this-&gt;resource()</code> and constructor arguments <code class="computeroutput">std::forward&lt;Args&gt;(args)...</code> is well-formed. [Note: uses-allocator construction is always well formed for types that do not use allocators. - end note]</p>
 109 <p><span class="bold"><strong>Effects</strong></span>: Construct a T object at p by uses-allocator construction with allocator <code class="computeroutput">this-&gt;resource()</code> and constructor arguments <code class="computeroutput">std::forward&lt;Args&gt;(args)...</code>.</p>
 110 <p><span class="bold"><strong>Throws</strong></span>: Nothing unless the constructor for T throws. </p>
 111 </li>
 112 <li class="listitem">
 113 <pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> U<span class="special">&gt;</span> <span class="keyword">void</span> <a name="idp50867920-bb"></a><span class="identifier">destroy</span><span class="special">(</span><span class="identifier">U</span> <span class="special">*</span> p<span class="special">)</span><span class="special">;</span></pre>
 114 <p><span class="bold"><strong>Effects</strong></span>: p-&gt;~U(). </p>
 115 </li>
 116 <li class="listitem">
 117 <pre class="literallayout"><a class="link" href="polymorphic_allocator.html" title="Class template polymorphic_allocator">polymorphic_allocator</a> <a name="idp50871280-bb"></a><span class="identifier">select_on_container_copy_construction</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>
 118 <p><span class="bold"><strong>Returns</strong></span>: Equivalent to <code class="computeroutput">polymorphic_allocator()</code>. </p>
 119 </li>
 120 <li class="listitem">
 121 <pre class="literallayout"><a class="link" href="memory_resource.html" title="Class memory_resource">memory_resource</a> <span class="special">*</span> <a name="idp50873968-bb"></a><span class="identifier">resource</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>
 122 <p><span class="bold"><strong>Returns</strong></span>: m_resource. </p>
 123 </li>
 124 </ol></div>
 125 </div>
 126 </div>
 127 </div>
 128 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 129 <td align="left"></td>
 130 <td align="right"><div class="copyright-footer">Copyright &#169; 2009-2015 Ion Gaztanaga<p>
 131         Distributed under the Boost Software License, Version 1.0. (See accompanying
 132         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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