<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> <title>Class template recursive_wrapper</title> <link rel="stylesheet" href="../../../doc/src/boostbook.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.78.1"> <link rel="home" href="../index.html" title="The Boost C++ Libraries BoostBook Documentation Subset"> <link rel="up" href="../variant/reference.html#header.boost.variant.recursive_wrapper_hpp" title="Header <boost/variant/recursive_wrapper.hpp>"> <link rel="prev" href="make_rec_idm45507101497936.html" title="Class template make_recursive_variant_over"> <link rel="next" href="is_recursive_wrapper.html" title="Class template is_recursive_wrapper"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table cellpadding="2" width="100%"><tr> <td valign="top"><img alt="Boost C++ 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name="boost.recursive_wrapper"></a><div class="titlepage"></div> <div class="refnamediv"> <h2><span class="refentrytitle">Class template recursive_wrapper</span></h2> <p>boost::recursive_wrapper — Solves circular dependencies, enabling recursive types.</p> </div> <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> <div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: <<a class="link" href="../variant/reference.html#header.boost.variant.recursive_wrapper_hpp" title="Header <boost/variant/recursive_wrapper.hpp>">boost/variant/recursive_wrapper.hpp</a>> </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="recursive_wrapper.html" title="Class template recursive_wrapper">recursive_wrapper</a> <span class="special">{</span> <span class="keyword">public</span><span class="special">:</span> <span class="comment">// types</span> <span class="keyword">typedef</span> <span class="identifier">T</span> <a name="boost.recursive_wrapper.type"></a><span class="identifier">type</span><span class="special">;</span> <span class="comment">// <a class="link" href="recursive_wrapper.html#boost.recursive_wrapperconstruct-copy-destruct">construct/copy/destruct</a></span> <a class="link" href="recursive_wrapper.html#idm45506893898464-bb"><span class="identifier">recursive_wrapper</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span> <a class="link" href="recursive_wrapper.html#idm45506895950048-bb"><span class="identifier">recursive_wrapper</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">recursive_wrapper</span> <span class="special">&</span><span class="special">)</span><span class="special">;</span> <a class="link" href="recursive_wrapper.html#idm45506897609024-bb"><span class="identifier">recursive_wrapper</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">T</span> <span class="special">&</span><span class="special">)</span><span class="special">;</span> <a class="link" href="recursive_wrapper.html#idm45506884861360-bb"><span class="special">~</span><span class="identifier">recursive_wrapper</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span> <span class="comment">// <a class="link" href="recursive_wrapper.html#idm45506892766144-bb">modifiers</a></span> <span class="keyword">void</span> <a class="link" href="recursive_wrapper.html#idm45506844729872-bb"><span class="identifier">swap</span></a><span class="special">(</span><span class="identifier">recursive_wrapper</span> <span class="special">&</span><span class="special">)</span><span class="special">;</span> <span class="identifier">recursive_wrapper</span> <span class="special">&</span> <a class="link" href="recursive_wrapper.html#idm45506889633888-bb"><span class="keyword">operator</span><span class="special">=</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">recursive_wrapper</span> <span class="special">&</span><span class="special">)</span><span class="special">;</span> <span class="identifier">recursive_wrapper</span> <span class="special">&</span> <a class="link" href="recursive_wrapper.html#idm45507159490512-bb"><span class="keyword">operator</span><span class="special">=</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">T</span> <span class="special">&</span><span class="special">)</span><span class="special">;</span> <span class="comment">// <a class="link" href="recursive_wrapper.html#idm45506845166496-bb">queries</a></span> <span class="identifier">T</span> <span class="special">&</span> <a class="link" href="recursive_wrapper.html#idm45507095230160-bb"><span class="identifier">get</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span> <span class="keyword">const</span> <span class="identifier">T</span> <span class="special">&</span> <a class="link" href="recursive_wrapper.html#idm45506993417520-bb"><span class="identifier">get</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> <span class="identifier">T</span> <span class="special">*</span> <a class="link" href="recursive_wrapper.html#idm45506845165792-bb"><span class="identifier">get_pointer</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span> <span class="keyword">const</span> <span class="identifier">T</span> <span class="special">*</span> <a class="link" href="recursive_wrapper.html#idm45506845164896-bb"><span class="identifier">get_pointer</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span> <span class="special">}</span><span class="special">;</span></pre></div> <div class="refsect1"> <a name="idm45555032343888"></a><h2>Description</h2> <p>The <code class="computeroutput">recursive_wrapper</code> class template has an interface similar to a simple value container, but its content is allocated dynamically. This allows <code class="computeroutput">recursive_wrapper</code> to hold types <code class="computeroutput">T</code> whose member data leads to a circular dependency (e.g., a data member of <code class="computeroutput">T</code> has a data member of type <code class="computeroutput">T</code>).</p> <p>The application of <code class="computeroutput">recursive_wrapper</code> is easiest understood in context. See <a class="xref" href="../variant/tutorial.html#variant.tutorial.recursive.recursive-wrapper" title="Recursive types with recursive_wrapper">the section called “Recursive types with <code class="computeroutput">recursive_wrapper</code>”</a> for a demonstration of a common use of the class template.</p> <p><span class="bold"><strong>Notes</strong></span>:</p> <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">Any type specified as the template argument to <code class="computeroutput">recursive_wrapper</code> must be capable of construction via <code class="computeroutput">operator new</code>. Thus, for instance, references are not supported.</li></ul></div> <div class="refsect2"> <a name="idm45555032333952"></a><h3> <a name="boost.recursive_wrapperconstruct-copy-destruct"></a><code class="computeroutput">recursive_wrapper</code> public construct/copy/destruct</h3> <div class="orderedlist"><ol class="orderedlist" type="1"> <li class="listitem"> <pre class="literallayout"><a name="idm45506893898464-bb"></a><span class="identifier">recursive_wrapper</span><span class="special">(</span><span class="special">)</span><span class="special">;</span></pre>Default constructor.<p class="simpara">Initializes <code class="computeroutput">*this</code> by default construction of <code class="computeroutput">T</code>.</p> <div class="variablelist"><table border="0" class="variablelist compact"> <colgroup> <col align="left" valign="top"> <col> </colgroup> <tbody> <tr> <td><p><span class="term">Requires:</span></p></td> <td> <code class="computeroutput">T</code> must fulfill the requirements of the <span class="emphasis"><em>DefaultConstructible</em></span> [20.1.4] concept.</td> </tr> <tr> <td><p><span class="term">Throws:</span></p></td> <td>May fail with any exceptions arising from the default constructor of <code class="computeroutput">T</code> or, in the event of insufficient memory, with <code class="computeroutput">std::bad_alloc</code>.</td> </tr> </tbody> </table></div> </li> <li class="listitem"> <pre class="literallayout"><a name="idm45506895950048-bb"></a><span class="identifier">recursive_wrapper</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">recursive_wrapper</span> <span class="special">&</span> other<span class="special">)</span><span class="special">;</span></pre>Copy constructor.<p class="simpara">Copies the content of <code class="computeroutput">other</code> into <code class="computeroutput">*this</code>.</p> <div class="variablelist"><table border="0" class="variablelist compact"> <colgroup> <col align="left" valign="top"> <col> </colgroup> <tbody><tr> <td><p><span class="term">Throws:</span></p></td> <td>May fail with any exceptions arising from the copy constructor of <code class="computeroutput">T</code> or, in the event of insufficient memory, with <code class="computeroutput">std::bad_alloc</code>.</td> </tr></tbody> </table></div> </li> <li class="listitem"> <pre class="literallayout"><a name="idm45506897609024-bb"></a><span class="identifier">recursive_wrapper</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">T</span> <span class="special">&</span> operand<span class="special">)</span><span class="special">;</span></pre>Value constructor.<p class="simpara">Copies <code class="computeroutput">operand</code> into <code class="computeroutput">*this</code>.</p> <div class="variablelist"><table border="0" class="variablelist compact"> <colgroup> <col align="left" valign="top"> <col> </colgroup> <tbody><tr> <td><p><span class="term">Throws:</span></p></td> <td>May fail with any exceptions arising from the copy constructor of <code class="computeroutput">T</code> or, in the event of insufficient memory, with <code class="computeroutput">std::bad_alloc</code>.</td> </tr></tbody> </table></div> </li> <li class="listitem"> <pre class="literallayout"><a name="idm45506884861360-bb"></a><span class="special">~</span><span class="identifier">recursive_wrapper</span><span class="special">(</span><span class="special">)</span><span class="special">;</span></pre>Destructor.<p class="simpara">Deletes the content of <code class="computeroutput">*this</code>.</p> <div class="variablelist"><table border="0" class="variablelist compact"> <colgroup> <col align="left" valign="top"> <col> </colgroup> <tbody><tr> <td><p><span class="term">Throws:</span></p></td> <td>Will not throw.</td> </tr></tbody> </table></div> </li> </ol></div> </div> <div class="refsect2"> <a name="idm45555032293984"></a><h3> <a name="idm45506892766144-bb"></a><code class="computeroutput">recursive_wrapper</code> modifiers</h3> <div class="orderedlist"><ol class="orderedlist" type="1"> <li class="listitem"> <pre class="literallayout"><span class="keyword">void</span> <a name="idm45506844729872-bb"></a><span class="identifier">swap</span><span class="special">(</span><span class="identifier">recursive_wrapper</span> <span class="special">&</span> other<span class="special">)</span><span class="special">;</span></pre> <p class="simpara">Exchanges contents of <code class="computeroutput">*this</code> and <code class="computeroutput">other</code>.</p> <div class="variablelist"><table border="0" class="variablelist compact"> <colgroup> <col align="left" valign="top"> <col> </colgroup> <tbody><tr> <td><p><span class="term">Throws:</span></p></td> <td>Will not throw.</td> </tr></tbody> </table></div> </li> <li class="listitem"> <pre class="literallayout"><span class="identifier">recursive_wrapper</span> <span class="special">&</span> <a name="idm45506889633888-bb"></a><span class="keyword">operator</span><span class="special">=</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">recursive_wrapper</span> <span class="special">&</span> rhs<span class="special">)</span><span class="special">;</span></pre>Copy assignment operator.<p class="simpara">Assigns the content of <code class="computeroutput">rhs</code> to the content of <code class="computeroutput">*this</code>.</p> <div class="variablelist"><table border="0" class="variablelist compact"> <colgroup> <col align="left" valign="top"> <col> </colgroup> <tbody> <tr> <td><p><span class="term">Requires:</span></p></td> <td> <code class="computeroutput">T</code> must fulfill the requirements of the Assignable concept.</td> </tr> <tr> <td><p><span class="term">Throws:</span></p></td> <td>May fail with any exceptions arising from the assignment operator of <code class="computeroutput">T</code>.</td> </tr> </tbody> </table></div> </li> <li class="listitem"> <pre class="literallayout"><span class="identifier">recursive_wrapper</span> <span class="special">&</span> <a name="idm45507159490512-bb"></a><span class="keyword">operator</span><span class="special">=</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">T</span> <span class="special">&</span> rhs<span class="special">)</span><span class="special">;</span></pre>Value assignment operator.<p class="simpara">Assigns <code class="computeroutput">rhs</code> into the content of <code class="computeroutput">*this</code>.</p> <div class="variablelist"><table border="0" class="variablelist compact"> <colgroup> <col align="left" valign="top"> <col> </colgroup> <tbody> <tr> <td><p><span class="term">Requires:</span></p></td> <td> <code class="computeroutput">T</code> must fulfill the requirements of the Assignable concept.</td> </tr> <tr> <td><p><span class="term">Throws:</span></p></td> <td>May fail with any exceptions arising from the assignment operator of <code class="computeroutput">T</code>.</td> </tr> </tbody> </table></div> </li> </ol></div> </div> <div class="refsect2"> <a name="idm45555032257200"></a><h3> <a name="idm45506845166496-bb"></a><code class="computeroutput">recursive_wrapper</code> queries</h3> <div class="orderedlist"><ol class="orderedlist" type="1"> <li class="listitem"> <pre class="literallayout"><a name="idm45507095230720-bb"></a><span class="identifier">T</span> <span class="special">&</span> <a name="idm45507095230160-bb"></a><span class="identifier">get</span><span class="special">(</span><span class="special">)</span><span class="special">;</span> <span class="keyword">const</span> <span class="identifier">T</span> <span class="special">&</span> <a name="idm45506993417520-bb"></a><span class="identifier">get</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre> <p class="simpara">Returns a reference to the content of <code class="computeroutput">*this</code>.</p> <div class="variablelist"><table border="0" class="variablelist compact"> <colgroup> <col align="left" valign="top"> <col> </colgroup> <tbody><tr> <td><p><span class="term">Throws:</span></p></td> <td>Will not throw.</td> </tr></tbody> </table></div> </li> <li class="listitem"> <pre class="literallayout"><a name="idm45506901400688-bb"></a><span class="identifier">T</span> <span class="special">*</span> <a name="idm45506845165792-bb"></a><span class="identifier">get_pointer</span><span class="special">(</span><span class="special">)</span><span class="special">;</span> <span class="keyword">const</span> <span class="identifier">T</span> <span class="special">*</span> <a name="idm45506845164896-bb"></a><span class="identifier">get_pointer</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre> <p class="simpara">Returns a pointer to the content of <code class="computeroutput">*this</code>.</p> <div class="variablelist"><table border="0" class="variablelist compact"> <colgroup> <col align="left" valign="top"> <col> </colgroup> <tbody><tr> <td><p><span class="term">Throws:</span></p></td> <td>Will not throw.</td> </tr></tbody> </table></div> </li> </ol></div> </div> </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 © 2002, 2003 Eric Friedman, Itay Maman<p>Distributed under the Boost Software License, Version 1.0. (See accompanying file <code class="filename">LICENSE_1_0.txt</code> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) </p> </div></td> </tr></table> <hr> <div class="spirit-nav"> <a accesskey="p" href="make_rec_idm45507101497936.html"><img src="../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../variant/reference.html#header.boost.variant.recursive_wrapper_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="is_recursive_wrapper.html"><img src="../../../doc/src/images/next.png" alt="Next"></a> </div> </body> </html>