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  24 </div>
  25 <div class="refentry">
  26 <a name="boost.recursive_wrapper"></a><div class="titlepage"></div>
  27 <div class="refnamediv">
  28 <h2><span class="refentrytitle">Class template recursive_wrapper</span></h2>
  29 <p>boost::recursive_wrapper &#8212; Solves circular dependencies, enabling recursive types.</p>
  30 </div>
  31 <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
  32 <div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="../variant/reference.html#header.boost.variant.recursive_wrapper_hpp" title="Header &lt;boost/variant/recursive_wrapper.hpp&gt;">boost/variant/recursive_wrapper.hpp</a>&gt;
  33
  34 </span><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">&gt;</span>
  35 <span class="keyword">class</span> <a class="link" href="recursive_wrapper.html" title="Class template recursive_wrapper">recursive_wrapper</a> <span class="special">{</span>
  36 <span class="keyword">public</span><span class="special">:</span>
  37   <span class="comment">// types</span>
  38   <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>
  39
  40   <span class="comment">// <a class="link" href="recursive_wrapper.html#boost.recursive_wrapperconstruct-copy-destruct">construct/copy/destruct</a></span>
  41   <a class="link" href="recursive_wrapper.html#idp300905104-bb"><span class="identifier">recursive_wrapper</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span>
  42   <a class="link" href="recursive_wrapper.html#idp306231216-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">&amp;</span><span class="special">)</span><span class="special">;</span>
  43   <a class="link" href="recursive_wrapper.html#idp300541232-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">&amp;</span><span class="special">)</span><span class="special">;</span>
  44   <a class="link" href="recursive_wrapper.html#idp150288000-bb"><span class="special">~</span><span class="identifier">recursive_wrapper</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span>
  45
  46   <span class="comment">// <a class="link" href="recursive_wrapper.html#idp222766320-bb">modifiers</a></span>
  47   <span class="keyword">void</span> <a class="link" href="recursive_wrapper.html#idp222766880-bb"><span class="identifier">swap</span></a><span class="special">(</span><span class="identifier">recursive_wrapper</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  48   <span class="identifier">recursive_wrapper</span> <span class="special">&amp;</span> <a class="link" href="recursive_wrapper.html#idp351567696-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">&amp;</span><span class="special">)</span><span class="special">;</span>
  49   <span class="identifier">recursive_wrapper</span> <span class="special">&amp;</span> <a class="link" href="recursive_wrapper.html#idp313623200-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">&amp;</span><span class="special">)</span><span class="special">;</span>
  50
  51   <span class="comment">// <a class="link" href="recursive_wrapper.html#idp213879504-bb">queries</a></span>
  52   <span class="identifier">T</span> <span class="special">&amp;</span> <a class="link" href="recursive_wrapper.html#idp213902160-bb"><span class="identifier">get</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span>
  53   <span class="keyword">const</span> <span class="identifier">T</span> <span class="special">&amp;</span> <a class="link" href="recursive_wrapper.html#idp213903056-bb"><span class="identifier">get</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  54   <span class="identifier">T</span> <span class="special">*</span> <a class="link" href="recursive_wrapper.html#idp213866864-bb"><span class="identifier">get_pointer</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span>
  55   <span class="keyword">const</span> <span class="identifier">T</span> <span class="special">*</span> <a class="link" href="recursive_wrapper.html#idp313842432-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>
  56 <span class="special">}</span><span class="special">;</span></pre></div>
  57 <div class="refsect1">
  58 <a name="idp524067600"></a><h2>Description</h2>
  59 <p>The <code class="computeroutput">recursive_wrapper</code> class template has an
  60           interface similar to a simple value container, but its content is
  61           allocated dynamically. This allows <code class="computeroutput">recursive_wrapper</code> to
  62           hold types <code class="computeroutput">T</code> whose member data leads to a circular
  63           dependency (e.g., a data member of <code class="computeroutput">T</code> has a data member
  64           of type <code class="computeroutput">T</code>).</p>
  65 <p>The application of <code class="computeroutput">recursive_wrapper</code> is easiest
  66           understood in context. See
  67           <a class="xref" href="../variant/tutorial.html#variant.tutorial.recursive.recursive-wrapper" title="Recursive types with recursive_wrapper">the section called &#8220;Recursive types with <code class="computeroutput">recursive_wrapper</code>&#8221;</a> for a
  68           demonstration of a common use of the class template.</p>
  69 <p><span class="bold"><strong>Notes</strong></span>:</p>
  70 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">Any type specified as the template argument to
  71             <code class="computeroutput">recursive_wrapper</code> must be capable of construction via
  72             <code class="computeroutput">operator new</code>. Thus, for instance, references are not
  73             supported.</li></ul></div>
  74 <div class="refsect2">
  75 <a name="idp524077536"></a><h3>
  76 <a name="boost.recursive_wrapperconstruct-copy-destruct"></a><code class="computeroutput">recursive_wrapper</code>
  77         public
  78        construct/copy/destruct</h3>
  79 <div class="orderedlist"><ol class="orderedlist" type="1">
  80 <li class="listitem">
  81 <pre class="literallayout"><a name="idp300905104-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
  82             <code class="computeroutput">T</code>.</p>
  83 <div class="variablelist"><table border="0" class="variablelist compact">
  84 <colgroup>
  85 <col align="left" valign="top">
  86 <col>
  87 </colgroup>
  88 <tbody>
  89 <tr>
  90 <td><p><span class="term">Requires:</span></p></td>
  91 <td>
  92 <code class="computeroutput">T</code> must fulfill the requirements of the
  93             <span class="emphasis"><em>DefaultConstructible</em></span> [20.1.4]
  94             concept.</td>
  95 </tr>
  96 <tr>
  97 <td><p><span class="term">Throws:</span></p></td>
  98 <td>May fail with any exceptions arising from the default
  99             constructor of <code class="computeroutput">T</code> or, in the event of
 100             insufficient memory, with <code class="computeroutput">std::bad_alloc</code>.</td>
 101 </tr>
 102 </tbody>
 103 </table></div>
 104 </li>
 105 <li class="listitem">
 106 <pre class="literallayout"><a name="idp306231216-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">&amp;</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
 107             <code class="computeroutput">*this</code>.</p>
 108 <div class="variablelist"><table border="0" class="variablelist compact">
 109 <colgroup>
 110 <col align="left" valign="top">
 111 <col>
 112 </colgroup>
 113 <tbody><tr>
 114 <td><p><span class="term">Throws:</span></p></td>
 115 <td>May fail with any exceptions arising from the
 116             copy constructor of <code class="computeroutput">T</code> or, in the event of
 117             insufficient memory, with <code class="computeroutput">std::bad_alloc</code>.</td>
 118 </tr></tbody>
 119 </table></div>
 120 </li>
 121 <li class="listitem">
 122 <pre class="literallayout"><a name="idp300541232-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">&amp;</span> operand<span class="special">)</span><span class="special">;</span></pre>Value constructor.<p class="simpara">Copies <code class="computeroutput">operand</code> into
 123             <code class="computeroutput">*this</code>.</p>
 124 <div class="variablelist"><table border="0" class="variablelist compact">
 125 <colgroup>
 126 <col align="left" valign="top">
 127 <col>
 128 </colgroup>
 129 <tbody><tr>
 130 <td><p><span class="term">Throws:</span></p></td>
 131 <td>May fail with any exceptions arising from the
 132             copy constructor of <code class="computeroutput">T</code> or, in the event of
 133             insufficient memory, with <code class="computeroutput">std::bad_alloc</code>.</td>
 134 </tr></tbody>
 135 </table></div>
 136 </li>
 137 <li class="listitem">
 138 <pre class="literallayout"><a name="idp150288000-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>
 139 <div class="variablelist"><table border="0" class="variablelist compact">
 140 <colgroup>
 141 <col align="left" valign="top">
 142 <col>
 143 </colgroup>
 144 <tbody><tr>
 145 <td><p><span class="term">Throws:</span></p></td>
 146 <td>Will not throw.</td>
 147 </tr></tbody>
 148 </table></div>
 149 </li>
 150 </ol></div>
 151 </div>
 152 <div class="refsect2">
 153 <a name="idp524117568"></a><h3>
 154 <a name="idp222766320-bb"></a><code class="computeroutput">recursive_wrapper</code> modifiers</h3>
 155 <div class="orderedlist"><ol class="orderedlist" type="1">
 156 <li class="listitem">
 157 <pre class="literallayout"><span class="keyword">void</span> <a name="idp222766880-bb"></a><span class="identifier">swap</span><span class="special">(</span><span class="identifier">recursive_wrapper</span> <span class="special">&amp;</span> other<span class="special">)</span><span class="special">;</span></pre>
 158 <p class="simpara">Exchanges contents of <code class="computeroutput">*this</code> and
 159               <code class="computeroutput">other</code>.</p>
 160 <div class="variablelist"><table border="0" class="variablelist compact">
 161 <colgroup>
 162 <col align="left" valign="top">
 163 <col>
 164 </colgroup>
 165 <tbody><tr>
 166 <td><p><span class="term">Throws:</span></p></td>
 167 <td>Will not throw.</td>
 168 </tr></tbody>
 169 </table></div>
 170 </li>
 171 <li class="listitem">
 172 <pre class="literallayout"><span class="identifier">recursive_wrapper</span> <span class="special">&amp;</span> <a name="idp351567696-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">&amp;</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
 173               <code class="computeroutput">*this</code>.</p>
 174 <div class="variablelist"><table border="0" class="variablelist compact">
 175 <colgroup>
 176 <col align="left" valign="top">
 177 <col>
 178 </colgroup>
 179 <tbody>
 180 <tr>
 181 <td><p><span class="term">Requires:</span></p></td>
 182 <td>
 183 <code class="computeroutput">T</code> must fulfill the requirements of
 184             the Assignable
 185             concept.</td>
 186 </tr>
 187 <tr>
 188 <td><p><span class="term">Throws:</span></p></td>
 189 <td>May fail with any exceptions arising from the assignment
 190               operator of <code class="computeroutput">T</code>.</td>
 191 </tr>
 192 </tbody>
 193 </table></div>
 194 </li>
 195 <li class="listitem">
 196 <pre class="literallayout"><span class="identifier">recursive_wrapper</span> <span class="special">&amp;</span> <a name="idp313623200-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">&amp;</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
 197               <code class="computeroutput">*this</code>.</p>
 198 <div class="variablelist"><table border="0" class="variablelist compact">
 199 <colgroup>
 200 <col align="left" valign="top">
 201 <col>
 202 </colgroup>
 203 <tbody>
 204 <tr>
 205 <td><p><span class="term">Requires:</span></p></td>
 206 <td>
 207 <code class="computeroutput">T</code> must fulfill the requirements of the
 208               Assignable
 209               concept.</td>
 210 </tr>
 211 <tr>
 212 <td><p><span class="term">Throws:</span></p></td>
 213 <td>May fail with any exceptions arising from the assignment
 214               operator of <code class="computeroutput">T</code>.</td>
 215 </tr>
 216 </tbody>
 217 </table></div>
 218 </li>
 219 </ol></div>
 220 </div>
 221 <div class="refsect2">
 222 <a name="idp524154288"></a><h3>
 223 <a name="idp213879504-bb"></a><code class="computeroutput">recursive_wrapper</code> queries</h3>
 224 <div class="orderedlist"><ol class="orderedlist" type="1">
 225 <li class="listitem">
 226 <pre class="literallayout"><a name="idp213901632-bb"></a><span class="identifier">T</span> <span class="special">&amp;</span> <a name="idp213902160-bb"></a><span class="identifier">get</span><span class="special">(</span><span class="special">)</span><span class="special">;</span>
 227 <span class="keyword">const</span> <span class="identifier">T</span> <span class="special">&amp;</span> <a name="idp213903056-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>
 228 <p class="simpara">Returns a reference to the content of
 229               <code class="computeroutput">*this</code>.</p>
 230 <div class="variablelist"><table border="0" class="variablelist compact">
 231 <colgroup>
 232 <col align="left" valign="top">
 233 <col>
 234 </colgroup>
 235 <tbody><tr>
 236 <td><p><span class="term">Throws:</span></p></td>
 237 <td>Will not throw.</td>
 238 </tr></tbody>
 239 </table></div>
 240 </li>
 241 <li class="listitem">
 242 <pre class="literallayout"><a name="idp213866416-bb"></a><span class="identifier">T</span> <span class="special">*</span> <a name="idp213866864-bb"></a><span class="identifier">get_pointer</span><span class="special">(</span><span class="special">)</span><span class="special">;</span>
 243 <span class="keyword">const</span> <span class="identifier">T</span> <span class="special">*</span> <a name="idp313842432-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>
 244 <p class="simpara">Returns a pointer to the content of
 245               <code class="computeroutput">*this</code>.</p>
 246 <div class="variablelist"><table border="0" class="variablelist compact">
 247 <colgroup>
 248 <col align="left" valign="top">
 249 <col>
 250 </colgroup>
 251 <tbody><tr>
 252 <td><p><span class="term">Throws:</span></p></td>
 253 <td>Will not throw.</td>
 254 </tr></tbody>
 255 </table></div>
 256 </li>
 257 </ol></div>
 258 </div>
 259 </div>
 260 </div>
 261 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 262 <td align="left"></td>
 263 <td align="right"><div class="copyright-footer">Copyright &#169; 2002, 2003 Eric Friedman, Itay Maman<p>Distributed under the Boost Software License, Version 1.0.
 264     (See accompanying file <code class="filename">LICENSE_1_0.txt</code> or copy at
 265     <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
 266     </p>
 267 </div></td>
 268 </tr></table>
 269 <hr>
 270 <div class="spirit-nav">
 271 <a accesskey="p" href="make_recursiv_idp351329984.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>
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