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| 26 | <div class="titlepage"><div> |
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| 27 | <div><h2 class="title"> |
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| 28 | <a name="ref"></a>Chapter 8. Boost.Ref</h2></div> |
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| 29 | <div><div class="author"><h3 class="author"> |
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| 30 | <span class="firstname">Jaakko</span> <span class="surname">Järvi</span> |
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| 31 | </h3></div></div> |
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| 32 | <div><div class="author"><h3 class="author"> |
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| 33 | <span class="firstname">Peter</span> <span class="surname">Dimov</span> |
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| 34 | </h3></div></div> |
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| 35 | <div><div class="author"><h3 class="author"> |
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| 36 | <span class="firstname">Douglas</span> <span class="surname">Gregor</span> |
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| 37 | </h3></div></div> |
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| 38 | <div><div class="author"><h3 class="author"> |
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| 39 | <span class="firstname">Dave</span> <span class="surname">Abrahams</span> |
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| 40 | </h3></div></div> |
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| 41 | <div><p class="copyright">Copyright © 1999, 2000 Jaakko Järvi</p></div> |
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| 42 | <div><p class="copyright">Copyright © 2001, 2002 Peter Dimov</p></div> |
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| 43 | <div><p class="copyright">Copyright © 2002 David Abrahams</p></div> |
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| 45 | <a name="id2730005"></a><p>Permission to copy, use, modify, sell and distribute this |
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| 49 | any purpose. |
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| 50 | </p> |
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| 51 | </div></div> |
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| 52 | </div></div> |
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| 53 | <div class="toc"> |
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| 54 | <p><b>Table of Contents</b></p> |
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| 55 | <dl> |
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| 56 | <dt><span class="section"><a href="ref.html#ref.intro">Introduction</a></span></dt> |
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| 57 | <dt><span class="section"><a href="ref/reference.html">Reference</a></span></dt> |
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| 58 | <dd><dl><dt><span class="section"><a href="ref/reference.html#header.boost.ref.hpp">Header <boost/ref.hpp></a></span></dt></dl></dd> |
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| 59 | <dt><span class="section"><a href="ref/ack.html">Acknowledgements</a></span></dt> |
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| 60 | </dl> |
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| 61 | </div> |
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| 62 | <div class="section" lang="en"> |
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| 63 | <div class="titlepage"><div><div><h3 class="title"> |
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| 64 | <a name="ref.intro"></a>Introduction</h3></div></div></div> |
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| 65 | <p>The Ref library is a small library that is useful for passing |
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| 66 | references to function templates (algorithms) that would usually |
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| 67 | take copies of their arguments. It defines the class template |
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| 68 | <code class="computeroutput"><a href="reference_wrapper.html" title="Class template reference_wrapper">boost::reference_wrapper<T></a></code>, |
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| 69 | the two functions |
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| 70 | <code class="computeroutput"><a href="reference_wrapper.html#id2366489">boost::ref</a></code> and |
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| 71 | <code class="computeroutput"><a href="reference_wrapper.html#cref">boost::cref</a></code> that return |
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| 72 | instances of <code class="computeroutput">boost::reference_wrapper<T></code>, and the |
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| 73 | two traits classes |
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| 74 | <code class="computeroutput"><a href="is_reference_wrapper.html" title="Class template is_reference_wrapper">boost::is_reference_wrapper<T></a></code> |
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| 75 | and |
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| 76 | <code class="computeroutput"><a href="unwrap_reference.html" title="Class template unwrap_reference">boost::unwrap_reference<T></a></code>.</p> |
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| 77 | <p>The purpose of |
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| 78 | <code class="computeroutput">boost::reference_wrapper<T></code> is to |
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| 79 | contain a reference to an object of type T. It is primarily used to |
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| 80 | "feed" references to function templates (algorithms) that take their |
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| 81 | parameter by value.</p> |
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| 82 | <p>To support this usage, |
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| 83 | <code class="computeroutput">boost::reference_wrapper<T></code> provides an implicit |
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| 84 | conversion to <code class="computeroutput">T&</code>. This usually allows the function |
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| 85 | templates to work on references unmodified.</p> |
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| 86 | <p><code class="computeroutput">boost::reference_wrapper<T></code> is |
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| 87 | both CopyConstructible and Assignable (ordinary references are not |
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| 88 | Assignable).</p> |
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| 89 | <p>The expression <code class="computeroutput">boost::ref(x)</code> |
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| 90 | returns a |
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| 91 | <code class="computeroutput">boost::reference_wrapper<X>(x)</code> where X |
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| 92 | is the type of x. Similarly, |
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| 93 | <code class="computeroutput">boost::cref(x)</code> returns a |
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| 94 | <code class="computeroutput">boost::reference_wrapper<X const>(x)</code>.</p> |
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| 95 | <p>The expression |
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| 96 | <code class="computeroutput">boost::is_reference_wrapper<T>::value</code> |
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| 97 | is true if T is a <code class="computeroutput">reference_wrapper</code>, and |
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| 98 | false otherwise.</p> |
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| 99 | <p>The type-expression |
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| 100 | <code class="computeroutput">boost::unwrap_reference<T>::type</code> is T::type if T |
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| 101 | is a <code class="computeroutput">reference_wrapper</code>, T otherwise.</p> |
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| 102 | </div> |
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| 103 | </div> |
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| 104 | <table width="100%"><tr> |
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| 105 | <td align="left"><small><p>Last revised: July 09, 2004 at 00:56:42 GMT</p></small></td> |
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