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<h2><span class="refentrytitle">Struct template constructible_with_allocator_prefix</span></h2>
<p>boost::container::constructible_with_allocator_prefix</p>
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<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
<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.uses_allocator_hpp" title="Header &lt;boost/container/uses_allocator.hpp&gt;">boost/container/uses_allocator.hpp</a>&gt;

</span><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">&gt;</span> 
<span class="keyword">struct</span> <a class="link" href="constructible__idp67501632.html" title="Struct template constructible_with_allocator_prefix">constructible_with_allocator_prefix</a> <span class="special">{</span>

  <span class="comment">// public data members</span>
  <span class="keyword">static</span> <span class="keyword">const</span> <span class="keyword">bool</span> <span class="identifier">value</span><span class="special">;</span>
<span class="special">}</span><span class="special">;</span></pre></div>
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<a name="id-1.3.10.12.42.4.4"></a><h2>Description</h2>
<p><span class="bold"><strong>Remark</strong></span>: if a specialization constructible_with_allocator_prefix&lt;X&gt;::value is true, indicates that T may be constructed with allocator_arg and T::allocator_type as its first two constructor arguments. Ideally, all constructors of T (including the copy and move constructors) should have a variant that accepts these two initial arguments.</p>
<p><span class="bold"><strong>Requires</strong></span>: specialization constructible_with_allocator_prefix&lt;X&gt;::value is true, T must have a nested type, allocator_type and at least one constructor for which allocator_arg_t is the first parameter and allocator_type is the second parameter. If not all constructors of T can be called with these initial arguments, and if T is used in a context where a container must call such a constructor, then the program is ill-formed.</p>
<p><code class="computeroutput"> template &lt;class T, class Allocator = allocator&lt;T&gt; &gt; class Y { public: typedef Allocator allocator_type;</code></p>
<p><code class="computeroutput"> // Default constructor with and allocator-extended default constructor Y(); Y(allocator_arg_t, const allocator_type&amp; a);</code></p>
<p><code class="computeroutput"> // Copy constructor and allocator-extended copy constructor Y(const Y&amp; yy); Y(allocator_arg_t, const allocator_type&amp; a, const Y&amp; yy);</code></p>
<p><code class="computeroutput"> // Variadic constructor and allocator-extended variadic constructor template&lt;class ...Args&gt; Y(Args&amp;&amp; args...); template&lt;class ...Args&gt; Y(allocator_arg_t, const allocator_type&amp; a, BOOST_FWD_REF(Args)... args); };</code></p>
<p><code class="computeroutput">// Specialize trait for class template Y template &lt;class T, class Allocator = allocator&lt;T&gt; &gt; struct <a class="link" href="constructible__idp67501632.html" title="Struct template constructible_with_allocator_prefix">constructible_with_allocator_prefix</a>&lt;Y&lt;T,Allocator&gt; &gt; { static const bool value = true; };</code></p>
<p><code class="computeroutput"></code></p>
<p><span class="bold"><strong>Note</strong></span>: This trait is a workaround inspired by "N2554: The Scoped Allocator Model (Rev 2)" (Pablo Halpern, 2008-02-29) to backport the scoped allocator model to C++03, as in C++03 there is no mechanism to detect if a type can be constructed from arbitrary arguments. Applications aiming portability with several compilers should always define this trait.</p>
<p>In conforming C++11 compilers or compilers supporting SFINAE expressions (when BOOST_NO_SFINAE_EXPR is NOT defined), this trait is ignored and C++11 rules will be used to detect if a type should be constructed with suffix or prefix allocator arguments. </p>
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        Distributed under the Boost Software License, Version 1.0. (See accompanying
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