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<title>Class template recursive_wrapper</title>
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<div class="refentry">
<a 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#idp777653552-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#idp777659856-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#idp777665632-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#idp777650864-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#idp777671392-bb">modifiers</a></span>
<span class="keyword">void</span> <a class="link" href="recursive_wrapper.html#idp777671952-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#idp777676528-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#idp777684224-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#idp777692064-bb">queries</a></span>
<span class="identifier">T</span> <span class="special">&</span> <a class="link" href="recursive_wrapper.html#idp777693184-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#idp777694080-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#idp777697792-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#idp777698688-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="idp615047856"></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="idp615057792"></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="idp777653552-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="idp777659856-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="idp777665632-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="idp777650864-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="idp615097824"></a><h3>
<a name="idp777671392-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="idp777671952-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="idp777676528-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 <a class="link" href="../Assignable.html" title="Concept Assignable">Assignable</a>
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="idp777684224-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
<a class="link" href="../Assignable.html" title="Concept Assignable">Assignable</a>
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="idp615136272"></a><h3>
<a name="idp777692064-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="idp777692624-bb"></a><span class="identifier">T</span> <span class="special">&</span> <a name="idp777693184-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="idp777694080-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="idp777697232-bb"></a><span class="identifier">T</span> <span class="special">*</span> <a name="idp777697792-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="idp777698688-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>
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