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| <div class="section"> |
| <div class="titlepage"><div><div><h2 class="title" style="clear: both"> |
| <a name="core.ref"></a><a class="link" href="ref.html" title="ref">ref</a> |
| </h2></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="ref.html#core.ref.introduction">Introduction</a></span></dt> |
| <dt><span class="section"><a href="ref.html#core.reference">Reference</a></span></dt> |
| <dt><span class="section"><a href="ref.html#core.ref.acknowledgments">Acknowledgments</a></span></dt> |
| </dl></div> |
| <div class="simplesect"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="idp86981712"></a>Authors</h3></div></div></div> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| Jaakko Järvi |
| </li> |
| <li class="listitem"> |
| Peter Dimov |
| </li> |
| <li class="listitem"> |
| Douglas Gregor |
| </li> |
| <li class="listitem"> |
| Dave Abrahams |
| </li> |
| <li class="listitem"> |
| Frank Mori Hess |
| </li> |
| <li class="listitem"> |
| Ronald Garcia |
| </li> |
| </ul></div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="core.ref.introduction"></a><a class="link" href="ref.html#core.ref.introduction" title="Introduction">Introduction</a> |
| </h3></div></div></div> |
| <p> |
| The Ref library is a small library that is useful for passing references |
| to function templates (algorithms) that would usually take copies of their |
| 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"><</span><span class="identifier">T</span><span class="special">></span></code>, |
| 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> |
| 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"><</span><span class="identifier">T</span><span class="special">></span></code>, |
| 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"><</span><span class="identifier">T</span><span class="special">></span></code> or |
| returns a reference to any other type of object, and the two traits classes |
| <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_reference_wrapper</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> and |
| <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">unwrap_reference</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code>. |
| </p> |
| <p> |
| The purpose of <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">reference_wrapper</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> is |
| to contain a reference to an object of type <code class="computeroutput"><span class="identifier">T</span></code>. |
| It is primarily used to "feed" references to function templates |
| (algorithms) that take their parameter by value. |
| </p> |
| <p> |
| 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"><</span><span class="identifier">T</span><span class="special">></span></code> |
| provides an implicit conversion to <code class="computeroutput"><span class="identifier">T</span><span class="special">&</span></code>. This usually allows the function templates |
| to work on references unmodified. |
| </p> |
| <p> |
| <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">reference_wrapper</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> is |
| both CopyConstructible and Assignable (ordinary references are not Assignable). |
| </p> |
| <p> |
| 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 |
| a <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">reference_wrapper</span><span class="special"><</span><span class="identifier">X</span><span class="special">>(</span><span class="identifier">x</span><span class="special">)</span></code> where |
| <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> |
| returns a <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">reference_wrapper</span><span class="special"><</span><span class="identifier">X</span> <span class="keyword">const</span><span class="special">>(</span><span class="identifier">x</span><span class="special">)</span></code>. |
| </p> |
| <p> |
| 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 |
| a <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">unwrap_reference</span><span class="special"><</span><span class="identifier">X</span><span class="special">>::</span><span class="identifier">type</span><span class="special">&</span></code> |
| where <code class="computeroutput"><span class="identifier">X</span></code> is the type of <code class="computeroutput"><span class="identifier">x</span></code>. |
| </p> |
| <p> |
| The expression <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_reference_wrapper</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">value</span></code> is <code class="computeroutput"><span class="keyword">true</span></code> |
| if <code class="computeroutput"><span class="identifier">T</span></code> is a <code class="computeroutput"><span class="identifier">reference_wrapper</span></code>, |
| and <code class="computeroutput"><span class="keyword">false</span></code> otherwise. |
| </p> |
| <p> |
| The type-expression <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">unwrap_reference</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</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> |
| if <code class="computeroutput"><span class="identifier">T</span></code> is a <code class="computeroutput"><span class="identifier">reference_wrapper</span></code>, |
| <code class="computeroutput"><span class="identifier">T</span></code> otherwise. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="core.reference"></a>Reference</h3></div></div></div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="header.boost.core.ref_hpp"></a>Header <<a href="../../../../../boost/core/ref.hpp" target="_top">boost/core/ref.hpp</a>></h4></div></div></div> |
| <pre class="synopsis"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">></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> |
| |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">></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> |
| |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">></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> |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">></span> <a class="link" href="../boost/reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a><span class="special"><</span> <span class="identifier">T</span> <span class="special">></span> <span class="keyword">const</span> <a class="link" href="../boost/ref_idp27531472.html" title="Function template ref"><span class="identifier">ref</span></a><span class="special">(</span><span class="identifier">T</span> <span class="special">&</span><span class="special">)</span><span class="special">;</span> |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">></span> <a class="link" href="../boost/reference_wrapper.html" title="Class template reference_wrapper">reference_wrapper</a><span class="special"><</span> <span class="identifier">T</span> <span class="keyword">const</span> <span class="special">></span> <span class="keyword">const</span> <a class="link" href="../boost/cref_idp27536288.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">&</span><span class="special">)</span><span class="special">;</span> |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">></span> <span class="keyword">void</span> <a class="link" href="../boost/ref_idp27541104.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">&&</span><span class="special">)</span><span class="special">;</span> |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">></span> <span class="keyword">void</span> <a class="link" href="../boost/cref_idp34566064.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">&&</span><span class="special">)</span><span class="special">;</span> |
| <span class="keyword">template</span><span class="special"><</span><span class="keyword">typename</span> T<span class="special">></span> <a class="link" href="../boost/unwrap_reference.html" title="Struct template unwrap_reference">unwrap_reference</a><span class="special"><</span> <span class="identifier">T</span> <span class="special">></span><span class="special">::</span><span class="identifier">type</span> <span class="special">&</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">&</span><span class="special">)</span><span class="special">;</span> |
| <span class="special">}</span></pre> |
| </div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="core.ref.acknowledgments"></a><a class="link" href="ref.html#core.ref.acknowledgments" title="Acknowledgments">Acknowledgments</a> |
| </h3></div></div></div> |
| <p> |
| <code class="computeroutput"><span class="identifier">ref</span></code> and <code class="computeroutput"><span class="identifier">cref</span></code> |
| were originally part of the Tuple library by Jaakko Järvi. They were |
| "promoted to <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span></code> |
| status" by Peter Dimov because they are generally useful. Douglas Gregor |
| and Dave Abrahams contributed <code class="computeroutput"><span class="identifier">is_reference_wrapper</span></code> |
| and <code class="computeroutput"><span class="identifier">unwrap_reference</span></code>. Frank |
| 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>. |
| </p> |
| </div> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2014 Peter Dimov<br>Copyright © 2014 Glen Fernandes<br>Copyright © 2014 Andrey Semashev<p> |
| Distributed under the <a href="http://boost.org/LICENSE_1_0.txt" target="_top">Boost |
| Software License, Version 1.0</a>. |
| </p> |
| </div></td> |
| </tr></table> |
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