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  24 </div>
  25 <div class="section">
  26 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
  27 <a name="core.ref"></a><a class="link" href="ref.html" title="ref">ref</a>
  28 </h2></div></div></div>
  29 <div class="toc"><dl class="toc">
  30 <dt><span class="section"><a href="ref.html#core.ref.introduction">Introduction</a></span></dt>
  31 <dt><span class="section"><a href="ref.html#core.reference">Reference</a></span></dt>
  32 <dt><span class="section"><a href="ref.html#core.ref.acknowledgments">Acknowledgments</a></span></dt>
  33 </dl></div>
  34 <div class="simplesect">
  35 <div class="titlepage"><div><div><h3 class="title">
  36 <a name="idm46687073876464"></a>Authors</h3></div></div></div>
  37 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  38 <li class="listitem">
  39           Jaakko J&#228;rvi
  40         </li>
  41 <li class="listitem">
  42           Peter Dimov
  43         </li>
  44 <li class="listitem">
  45           Douglas Gregor
  46         </li>
  47 <li class="listitem">
  48           Dave Abrahams
  49         </li>
  50 <li class="listitem">
  51           Frank Mori Hess
  52         </li>
  53 <li class="listitem">
  54           Ronald Garcia
  55         </li>
  56 </ul></div>
  57 </div>
  58 <div class="section">
  59 <div class="titlepage"><div><div><h3 class="title">
  60 <a name="core.ref.introduction"></a><a class="link" href="ref.html#core.ref.introduction" title="Introduction">Introduction</a>
  61 </h3></div></div></div>
  62 <p>
  63         The Ref library is a small library that is useful for passing references
  64         to function templates (algorithms) that would usually take copies of their
  65         arguments. It defines the class template <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">reference_wrapper</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>,
  66         two functions <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">ref</span></code> and <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">cref</span></code>
  67         that return instances of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">reference_wrapper</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>,
  68         a function <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">unwrap_ref</span></code> that unwraps a <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">reference_wrapper</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> or
  69         returns a reference to any other type of object, and the two traits classes
  70         <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_reference_wrapper</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> and
  71         <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">unwrap_reference</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>.
  72       </p>
  73 <p>
  74         The purpose of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">reference_wrapper</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> is
  75         to contain a reference to an object of type <code class="computeroutput"><span class="identifier">T</span></code>.
  76         It is primarily used to "feed" references to function templates
  77         (algorithms) that take their parameter by value.
  78       </p>
  79 <p>
  80         To support this usage, <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">reference_wrapper</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>
  81         provides an implicit conversion to <code class="computeroutput"><span class="identifier">T</span><span class="special">&amp;</span></code>. This usually allows the function templates
  82         to work on references unmodified.
  83       </p>
  84 <p>
  85         <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">reference_wrapper</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code> is
  86         both CopyConstructible and Assignable (ordinary references are not Assignable).
  87       </p>
  88 <p>
  89         The <code class="computeroutput"><span class="identifier">expression</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">ref</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span></code> returns
  90         a <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">reference_wrapper</span><span class="special">&lt;</span><span class="identifier">X</span><span class="special">&gt;(</span><span class="identifier">x</span><span class="special">)</span></code> where
  91         <code class="computeroutput"><span class="identifier">X</span></code> is the type of <code class="computeroutput"><span class="identifier">x</span></code>. Similarly, <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">cref</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span></code>
  92         returns a <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">reference_wrapper</span><span class="special">&lt;</span><span class="identifier">X</span> <span class="keyword">const</span><span class="special">&gt;(</span><span class="identifier">x</span><span class="special">)</span></code>.
  93       </p>
  94 <p>
  95         The expression <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">unwrap_ref</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span></code> returns
  96         a <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">unwrap_reference</span><span class="special">&lt;</span><span class="identifier">X</span><span class="special">&gt;::</span><span class="identifier">type</span><span class="special">&amp;</span></code>
  97         where <code class="computeroutput"><span class="identifier">X</span></code> is the type of <code class="computeroutput"><span class="identifier">x</span></code>.
  98       </p>
  99 <p>
 100         The expression <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_reference_wrapper</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">value</span></code> is <code class="computeroutput"><span class="keyword">true</span></code>
 101         if <code class="computeroutput"><span class="identifier">T</span></code> is a <code class="computeroutput"><span class="identifier">reference_wrapper</span></code>,
 102         and <code class="computeroutput"><span class="keyword">false</span></code> otherwise.
 103       </p>
 104 <p>
 105         The type-expression <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">unwrap_reference</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;::</span><span class="identifier">type</span></code> is <code class="computeroutput"><span class="identifier">T</span><span class="special">::</span><span class="identifier">type</span></code>
 106         if <code class="computeroutput"><span class="identifier">T</span></code> is a <code class="computeroutput"><span class="identifier">reference_wrapper</span></code>,
 107         <code class="computeroutput"><span class="identifier">T</span></code> otherwise.
 108       </p>
 109 </div>
 110 <div class="section">
 111 <div class="titlepage"><div><div><h3 class="title">
 112 <a name="core.reference"></a>Reference</h3></div></div></div>
 113 <div class="section">
 114 <div class="titlepage"><div><div><h4 class="title">
 115 <a name="header.boost.core.ref_hpp"></a>Header &lt;<a href="../../../../../boost/core/ref.hpp" target="_top">boost/core/ref.hpp</a>&gt;</h4></div></div></div>
 116 <pre class="synopsis"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span>
 117   <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="../boost/is_reference_wrapper.html" title="Struct template is_reference_wrapper">is_reference_wrapper</a><span class="special">;</span>
 118
 119   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">&gt;</span> <span class="keyword">class</span> <a class="link" href="../boost/reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a><span class="special">;</span>
 120
 121   <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="../boost/unwrap_reference.html" title="Struct template unwrap_reference">unwrap_reference</a><span class="special">;</span>
 122   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">&gt;</span> <a class="link" href="../boost/reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a><span class="special">&lt;</span> <span class="identifier">T</span> <span class="special">&gt;</span> <span class="keyword">const</span> <a class="link" href="../boost/ref_idm45818739683584.html" title="Function template ref"><span class="identifier">ref</span></a><span class="special">(</span><span class="identifier">T</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
 123   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">&gt;</span> <a class="link" href="../boost/reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a><span class="special">&lt;</span> <span class="identifier">T</span> <span class="keyword">const</span>  <span class="special">&gt;</span> <span class="keyword">const</span> <a class="link" href="../boost/cref_idm45818739678608.html" title="Function template cref"><span class="identifier">cref</span></a><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
 124   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">&gt;</span> <span class="keyword">void</span> <a class="link" href="../boost/ref_idm45818729534336.html" title="Function template ref"><span class="identifier">ref</span></a><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span> <span class="special">&amp;&amp;</span><span class="special">)</span><span class="special">;</span>
 125   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">&gt;</span> <span class="keyword">void</span> <a class="link" href="../boost/cref_idm45818729531568.html" title="Function template cref"><span class="identifier">cref</span></a><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span> <span class="special">&amp;&amp;</span><span class="special">)</span><span class="special">;</span>
 126   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">&gt;</span> <a class="link" href="../boost/unwrap_reference.html" title="Struct template unwrap_reference">unwrap_reference</a><span class="special">&lt;</span> <span class="identifier">T</span> <span class="special">&gt;</span><span class="special">::</span><span class="identifier">type</span> <span class="special">&amp;</span> <a class="link" href="../boost/unwrap_ref.html" title="Function template unwrap_ref"><span class="identifier">unwrap_ref</span></a><span class="special">(</span><span class="identifier">T</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
 127 <span class="special">}</span></pre>
 128 </div>
 129 </div>
 130 <div class="section">
 131 <div class="titlepage"><div><div><h3 class="title">
 132 <a name="core.ref.acknowledgments"></a><a class="link" href="ref.html#core.ref.acknowledgments" title="Acknowledgments">Acknowledgments</a>
 133 </h3></div></div></div>
 134 <p>
 135         <code class="computeroutput"><span class="identifier">ref</span></code> and <code class="computeroutput"><span class="identifier">cref</span></code>
 136         were originally part of the Tuple library by Jaakko J&#228;rvi. They were
 137         "promoted to <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span></code>
 138         status" by Peter Dimov because they are generally useful. Douglas Gregor
 139         and Dave Abrahams contributed <code class="computeroutput"><span class="identifier">is_reference_wrapper</span></code>
 140         and <code class="computeroutput"><span class="identifier">unwrap_reference</span></code>. Frank
 141         Mori Hess and Ronald Garcia contributed <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">unwrap_ref</span></code>.
 142       </p>
 143 </div>
 144 </div>
 145 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 146 <td align="left"></td>
 147 <td align="right"><div class="copyright-footer">Copyright &#169; 2014 Peter Dimov<br>Copyright &#169; 2014 Glen Fernandes<br>Copyright &#169; 2014 Andrey Semashev<p>
 148         Distributed under the <a href="http://boost.org/LICENSE_1_0.txt" target="_top">Boost
 149         Software License, Version 1.0</a>.
 150       </p>
 151 </div></td>
 152 </tr></table>
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