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163 lines
3.9 KiB
HTML
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<title>Boost: ref.hpp documentation</title>
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<body bgcolor="White">
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<table border="0" width="100%">
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<tr>
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<img src="../../c++boost.gif" alt="c++boost.gif (8819 bytes)" width="277" height="86">
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</td>
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<td align="center">
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<table border="0">
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<tr><td nowrap><h1>ref.hpp</h1></td></tr>
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<tr><td align="right" nowrap><small> 1.00.0003 (2001-08-22)</small></td></tr>
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</table>
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</td>
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</tr>
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<tr>
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<td colspan="2" height="64"> </td>
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</tr>
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</table>
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<h2>Files</h2>
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<ul>
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<li><a href="../../boost/ref.hpp">ref.hpp</a>
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</ul>
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<h2>Purpose</h2>
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<p>
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The header <a href="../../boost/ref.hpp">boost/ref.hpp</a> defines the class template
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<b>boost::reference_wrapper<T></b> and the two functions <b>boost::ref</b> and
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<b>boost::cref</b> that return instances of <b>boost::reference_wrapper<T></b>.
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</p>
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<p>
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The purpose of <b>boost::reference_wrapper<T></b> is to contain a reference to
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an object of type <b>T</b>. It is primarily used to "feed" references to
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function templates (algorithms) that take their parameter by value.
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</p>
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<p>
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To support this usage, <b>boost::reference_wrapper<T></b> provides an implicit
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conversion to <b>T &</b>. This usually allows the function templates to
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work on references unmodified.
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</p>
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<p>
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<b>boost::reference_wrapper<T></b> is <b>CopyConstructible</b>, but it is not
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<b>Assignable</b>.
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</p>
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<p>
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The expression <b>boost::ref(x)</b> returns a <b>boost::reference_wrapper<X>(x)</b>
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where <b>X</b> is the type of <b>x</b>. Similarly, <b>boost::cref(x)</b>
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returns a <b>boost::reference_wrapper<X const>(x)</b>.
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</p>
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<h2>Interface</h2>
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<h3>Synopsis</h3>
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<pre>
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namespace boost
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{
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template<class T> class <a href="#reference_wrapper">reference_wrapper</a>;
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template<class T> reference_wrapper<T> <a href="#ref">ref</a>(T & t);
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template<class T> reference_wrapper<T const> <a href="#cref">cref</a>(T const & t);
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}
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</pre>
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<h3><a name="reference_wrapper">reference_wrapper</a></h3>
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<pre>
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template<class T> class reference_wrapper
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{
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public:
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explicit <a href="#rt_construct">reference_wrapper</a>(T & t);
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<a href="#rt_operator">operator T &</a> () const;
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T & <a href="#rt_get">get</a>() const;
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};
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</pre>
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<h4><a name="rt_construct">explicit reference_wrapper(T & t)</a></h4>
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<p>
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<b>Effects:</b> Constructs a <b>reference_wrapper</b> object that stores a reference to <b>t</b>.
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</p>
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<p>
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<b>Throws:</b> Nothing.
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</p>
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<h4><a name="rt_operator">operator T & () const</a></h4>
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<p>
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<b>Returns:</b> the stored reference.
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</p>
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<p>
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<b>Throws:</b> Nothing.
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</p>
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<h4><a name="rt_get">T & get() const</a></h4>
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<p>
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<b>Returns:</b> the stored reference.
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</p>
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<p>
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<b>Throws:</b> Nothing.
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</p>
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<h3><a name="ref">ref</a></h3>
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<pre>
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template<class T> reference_wrapper<T> ref(T & t);
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</pre>
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<p>
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<b>Returns:</b> <tt>reference_wrapper<T>(t)</tt>.
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</p>
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<p>
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<b>Throws:</b> Nothing.
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</p>
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<h3><a name="cref">cref</a></h3>
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<pre>
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template<class T> reference_wrapper<T const> cref(T const & t);
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</pre>
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<p>
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<b>Returns:</b> <tt>reference_wrapper<T const>(t)</tt>.
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</p>
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<p>
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<b>Throws:</b> Nothing.
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</p>
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<h2>Acknowledgements</h2>
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<p>
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<b>ref</b> and <b>cref</b> were originally part of the Boost.Tuple library.
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They were "promoted to <b>boost::</b> status" because they are generally
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useful.
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</p>
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<p><br><br><br><small>Copyright © 2001 by Peter Dimov and Multi Media
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Ltd. Permission to copy, use, modify, sell and distribute this document is
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granted provided this copyright notice appears in all copies. This document
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is provided "as is" without express or implied warranty, and with
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no claim as to its suitability for any purpose.</small></p>
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</body>
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</html>
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