doc/html/boost/container/construc_idm45836563857392.html

   1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
   2 <html>
   3 <head>
   4 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
   5 <title>Struct template constructible_with_allocator_prefix</title>
   6 <link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css">
   7 <meta name="generator" content="DocBook XSL Stylesheets V1.79.1">
   8 <link rel="home" href="../../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset">
   9 <link rel="up" href="../../boost_container_header_reference.html#header.boost.container.uses_allocator_hpp" title="Header &lt;boost/container/uses_allocator.hpp&gt;">
  10 <link rel="prev" href="throw_runtime_error.html" title="Function throw_runtime_error">
  11 <link rel="next" href="construc_idm45836563847024.html" title="Struct template constructible_with_allocator_suffix">
  12 </head>
  13 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
  14 <table cellpadding="2" width="100%"><tr>
  15 <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td>
  16 <td align="center"><a href="../../../../index.html">Home</a></td>
  17 <td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td>
  18 <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
  19 <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
  20 <td align="center"><a href="../../../../more/index.htm">More</a></td>
  21 </tr></table>
  22 <hr>
  23 <div class="spirit-nav">
  24 <a accesskey="p" href="throw_runtime_error.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../boost_container_header_reference.html#header.boost.container.uses_allocator_hpp"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="construc_idm45836563847024.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
  25 </div>
  26 <div class="refentry">
  27 <a name="boost.container.construc_idm45836563857392"></a><div class="titlepage"></div>
  28 <div class="refnamediv">
  29 <h2><span class="refentrytitle">Struct template constructible_with_allocator_prefix</span></h2>
  30 <p>boost::container::constructible_with_allocator_prefix</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.uses_allocator_hpp" title="Header &lt;boost/container/uses_allocator.hpp&gt;">boost/container/uses_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">struct</span> <a class="link" href="construc_idm45836563857392.html" title="Struct template constructible_with_allocator_prefix">constructible_with_allocator_prefix</a> <span class="special">{</span>
  37
  38   <span class="comment">// public data members</span>
  39   <span class="keyword">static</span> <span class="keyword">const</span> <span class="keyword">bool</span> <span class="identifier">value</span><span class="special">;</span>
  40 <span class="special">}</span><span class="special">;</span></pre></div>
  41 <div class="refsect1">
  42 <a name="id-1.3.10.14.42.3.4"></a><h2>Description</h2>
  43 <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>
  44 <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>
  45 <p><code class="computeroutput"> template &lt;class T, class Allocator = allocator&lt;T&gt; &gt; class Y { public: typedef Allocator allocator_type;</code></p>
  46 <p><code class="computeroutput"> // Default constructor with and allocator-extended default constructor Y(); Y(allocator_arg_t, const allocator_type&amp; a);</code></p>
  47 <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>
  48 <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>
  49 <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="construc_idm45836563857392.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>
  50 <p><code class="computeroutput"></code></p>
  51 <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>
  52 <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>
  53 </div>
  54 </div>
  55 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
  56 <td align="left"></td>
  57 <td align="right"><div class="copyright-footer">Copyright &#169; 2009-2018 Ion Gaztanaga<p>
  58         Distributed under the Boost Software License, Version 1.0. (See accompanying
  59         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>)
  60       </p>
  61 </div></td>
  62 </tr></table>
  63 <hr>
  64 <div class="spirit-nav">
  65 <a accesskey="p" href="throw_runtime_error.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../boost_container_header_reference.html#header.boost.container.uses_allocator_hpp"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="construc_idm45836563847024.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
  66 </div>
  67 </body>
  68 </html>