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  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="fusion.support.pair"></a><a class="link" href="pair.html" title="pair">pair</a>
  28 </h3></div></div></div>
  29 <h5>
  30 <a name="fusion.support.pair.h0"></a>
  31         <span><a name="fusion.support.pair.description"></a></span><a class="link" href="pair.html#fusion.support.pair.description">Description</a>
  32       </h5>
  33 <p>
  34         Fusion <code class="computeroutput"><span class="identifier">pair</span></code> type is a half
  35         runtime pair. A half runtime pair is similar to a <a class="link" href="../adapted/std__pair.html" title="std::pair"><code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span></code></a>,
  36         but, unlike <a class="link" href="../adapted/std__pair.html" title="std::pair"><code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span></code></a>,
  37         the first type does not have data. It is used as elements in <a class="link" href="../container/map.html" title="map"><code class="computeroutput"><span class="identifier">map</span></code></a>s, for example.
  38       </p>
  39 <h5>
  40 <a name="fusion.support.pair.h1"></a>
  41         <span><a name="fusion.support.pair.synopsis"></a></span><a class="link" href="pair.html#fusion.support.pair.synopsis">Synopsis</a>
  42       </h5>
  43 <pre class="programlisting"><span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">First</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Second</span><span class="special">&gt;</span>
  44 <span class="keyword">struct</span> <span class="identifier">pair</span><span class="special">;</span>
  45
  46 <span class="keyword">namespace</span> <span class="identifier">result_of</span>
  47 <span class="special">{</span>
  48     <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Pair</span><span class="special">&gt;</span>
  49     <span class="keyword">struct</span> <span class="identifier">first</span><span class="special">;</span>
  50
  51     <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Pair</span><span class="special">&gt;</span>
  52     <span class="keyword">struct</span> <span class="identifier">second</span><span class="special">;</span>
  53
  54     <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">First</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Second</span><span class="special">&gt;</span>
  55     <span class="keyword">struct</span> <span class="identifier">make_pair</span><span class="special">;</span>
  56 <span class="special">}</span>
  57
  58 <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">First</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Second</span><span class="special">&gt;</span>
  59 <span class="keyword">typename</span> <span class="identifier">result_of</span><span class="special">::</span><span class="identifier">make_pair</span><span class="special">&lt;</span><span class="identifier">First</span><span class="special">,</span><span class="identifier">Second</span><span class="special">&gt;::</span><span class="identifier">type</span>
  60 <span class="identifier">make_pair</span><span class="special">(</span><span class="identifier">Second</span> <span class="keyword">const</span> <span class="special">&amp;);</span>
  61 </pre>
  62 <h5>
  63 <a name="fusion.support.pair.h2"></a>
  64         <span><a name="fusion.support.pair.template_parameters"></a></span><a class="link" href="pair.html#fusion.support.pair.template_parameters">Template
  65         parameters</a>
  66       </h5>
  67 <div class="informaltable"><table class="table">
  68 <colgroup>
  69 <col>
  70 <col>
  71 </colgroup>
  72 <thead><tr>
  73 <th>
  74                 <p>
  75                   Parameter
  76                 </p>
  77               </th>
  78 <th>
  79                 <p>
  80                   Description
  81                 </p>
  82               </th>
  83 </tr></thead>
  84 <tbody>
  85 <tr>
  86 <td>
  87                 <p>
  88                   First
  89                 </p>
  90               </td>
  91 <td>
  92                 <p>
  93                   The first type. This is purely a type. No data is held.
  94                 </p>
  95               </td>
  96 </tr>
  97 <tr>
  98 <td>
  99                 <p>
 100                   Second
 101                 </p>
 102               </td>
 103 <td>
 104                 <p>
 105                   The second type. This contains data.
 106                 </p>
 107               </td>
 108 </tr>
 109 </tbody>
 110 </table></div>
 111 <div class="variablelist">
 112 <p class="title"><b>Notation</b></p>
 113 <dl>
 114 <dt><span class="term"><code class="computeroutput"><span class="identifier">P</span></code></span></dt>
 115 <dd><p>
 116               Fusion pair type
 117             </p></dd>
 118 <dt><span class="term"><code class="computeroutput"><span class="identifier">p</span></code>, <code class="computeroutput"><span class="identifier">p2</span></code></span></dt>
 119 <dd><p>
 120               Fusion pairs
 121             </p></dd>
 122 <dt><span class="term"><code class="computeroutput"><span class="identifier">F</span></code>, <code class="computeroutput"><span class="identifier">S</span></code></span></dt>
 123 <dd><p>
 124               Arbitrary types
 125             </p></dd>
 126 <dt><span class="term"><code class="computeroutput"><span class="identifier">s</span></code></span></dt>
 127 <dd><p>
 128               Value of type <code class="computeroutput"><span class="identifier">S</span></code>
 129             </p></dd>
 130 <dt><span class="term"><code class="computeroutput"><span class="identifier">o</span></code></span></dt>
 131 <dd><p>
 132               Output stream
 133             </p></dd>
 134 <dt><span class="term"><code class="computeroutput"><span class="identifier">i</span></code></span></dt>
 135 <dd><p>
 136               Input stream
 137             </p></dd>
 138 </dl>
 139 </div>
 140 <h5>
 141 <a name="fusion.support.pair.h3"></a>
 142         <span><a name="fusion.support.pair.expression_semantics"></a></span><a class="link" href="pair.html#fusion.support.pair.expression_semantics">Expression
 143         Semantics</a>
 144       </h5>
 145 <div class="informaltable"><table class="table">
 146 <colgroup>
 147 <col>
 148 <col>
 149 </colgroup>
 150 <thead><tr>
 151 <th>
 152                 <p>
 153                   Expression
 154                 </p>
 155               </th>
 156 <th>
 157                 <p>
 158                   Semantics
 159                 </p>
 160               </th>
 161 </tr></thead>
 162 <tbody>
 163 <tr>
 164 <td>
 165                 <p>
 166                   <code class="computeroutput"><span class="identifier">P</span><span class="special">::</span><span class="identifier">first_type</span></code>
 167                 </p>
 168               </td>
 169 <td>
 170                 <p>
 171                   The type of the first template parameter, <code class="computeroutput"><span class="identifier">F</span></code>,
 172                   equivalent to <code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">first</span><span class="special">&lt;</span><span class="identifier">P</span><span class="special">&gt;::</span><span class="identifier">type</span></code>.
 173                 </p>
 174               </td>
 175 </tr>
 176 <tr>
 177 <td>
 178                 <p>
 179                   <code class="computeroutput"><span class="identifier">P</span><span class="special">::</span><span class="identifier">second_type</span></code>
 180                 </p>
 181               </td>
 182 <td>
 183                 <p>
 184                   The type of the second template parameter, <code class="computeroutput"><span class="identifier">S</span></code>,
 185                   equivalent to <code class="computeroutput"><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">second</span><span class="special">&lt;</span><span class="identifier">P</span><span class="special">&gt;::</span><span class="identifier">type</span></code>.
 186                 </p>
 187               </td>
 188 </tr>
 189 <tr>
 190 <td>
 191                 <p>
 192                   <code class="computeroutput"><span class="identifier">P</span><span class="special">()</span></code>
 193                 </p>
 194               </td>
 195 <td>
 196                 <p>
 197                   Default construction.
 198                 </p>
 199               </td>
 200 </tr>
 201 <tr>
 202 <td>
 203                 <p>
 204                   <code class="computeroutput"><span class="identifier">P</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span></code>
 205                 </p>
 206               </td>
 207 <td>
 208                 <p>
 209                   Construct a pair given value for the second type, <code class="computeroutput"><span class="identifier">s</span></code>.
 210                 </p>
 211               </td>
 212 </tr>
 213 <tr>
 214 <td>
 215                 <p>
 216                   <code class="computeroutput"><span class="identifier">P</span><span class="special">(</span><span class="identifier">p2</span><span class="special">)</span></code>
 217                 </p>
 218               </td>
 219 <td>
 220                 <p>
 221                   Copy constructs a pair from another pair, <code class="computeroutput"><span class="identifier">p2</span></code>.
 222                 </p>
 223               </td>
 224 </tr>
 225 <tr>
 226 <td>
 227                 <p>
 228                   <code class="computeroutput"><span class="identifier">p</span><span class="special">.</span><span class="identifier">second</span></code>
 229                 </p>
 230               </td>
 231 <td>
 232                 <p>
 233                   Get the data from <code class="computeroutput"><span class="identifier">p1</span></code>.
 234                 </p>
 235               </td>
 236 </tr>
 237 <tr>
 238 <td>
 239                 <p>
 240                   <code class="computeroutput"><span class="identifier">p</span> <span class="special">=</span>
 241                   <span class="identifier">p2</span></code>
 242                 </p>
 243               </td>
 244 <td>
 245                 <p>
 246                   Assigns a pair, <code class="computeroutput"><span class="identifier">p1</span></code>,
 247                   from another pair, <code class="computeroutput"><span class="identifier">p2</span></code>.
 248                 </p>
 249               </td>
 250 </tr>
 251 <tr>
 252 <td>
 253                 <p>
 254                   make_pair&lt;F&gt;(s)
 255                 </p>
 256               </td>
 257 <td>
 258                 <p>
 259                   Make a pair given the first type, <code class="computeroutput"><span class="identifier">F</span></code>,
 260                   and a value for the second type, <code class="computeroutput"><span class="identifier">s</span></code>.
 261                   The second type assumes the type of <code class="computeroutput"><span class="identifier">s</span></code>
 262                 </p>
 263               </td>
 264 </tr>
 265 <tr>
 266 <td>
 267                 <p>
 268                   <code class="computeroutput"><span class="identifier">o</span> <span class="special">&lt;&lt;</span>
 269                   <span class="identifier">p</span></code>
 270                 </p>
 271               </td>
 272 <td>
 273                 <p>
 274                   Output <code class="computeroutput"><span class="identifier">p</span></code> to output
 275                   stream, <code class="computeroutput"><span class="identifier">o</span></code>.
 276                 </p>
 277               </td>
 278 </tr>
 279 <tr>
 280 <td>
 281                 <p>
 282                   <code class="computeroutput"><span class="identifier">i</span> <span class="special">&gt;&gt;</span>
 283                   <span class="identifier">p</span></code>
 284                 </p>
 285               </td>
 286 <td>
 287                 <p>
 288                   Input <code class="computeroutput"><span class="identifier">p</span></code> from input
 289                   stream, <code class="computeroutput"><span class="identifier">i</span></code>.
 290                 </p>
 291               </td>
 292 </tr>
 293 <tr>
 294 <td>
 295                 <p>
 296                   <code class="computeroutput"><span class="identifier">p</span> <span class="special">==</span>
 297                   <span class="identifier">p2</span></code>
 298                 </p>
 299               </td>
 300 <td>
 301                 <p>
 302                   Tests two pairs for equality.
 303                 </p>
 304               </td>
 305 </tr>
 306 <tr>
 307 <td>
 308                 <p>
 309                   <code class="computeroutput"><span class="identifier">p</span> <span class="special">!=</span>
 310                   <span class="identifier">p2</span></code>
 311                 </p>
 312               </td>
 313 <td>
 314                 <p>
 315                   Tests two pairs for inequality.
 316                 </p>
 317               </td>
 318 </tr>
 319 </tbody>
 320 </table></div>
 321 <h5>
 322 <a name="fusion.support.pair.h4"></a>
 323         <span><a name="fusion.support.pair.header"></a></span><a class="link" href="pair.html#fusion.support.pair.header">Header</a>
 324       </h5>
 325 <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">support</span><span class="special">/</span><span class="identifier">pair</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 326 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">pair</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 327 </pre>
 328 <h5>
 329 <a name="fusion.support.pair.h5"></a>
 330         <span><a name="fusion.support.pair.example"></a></span><a class="link" href="pair.html#fusion.support.pair.example">Example</a>
 331       </h5>
 332 <pre class="programlisting"><span class="identifier">pair</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">,</span> <span class="keyword">char</span><span class="special">&gt;</span> <span class="identifier">p</span><span class="special">(</span><span class="char">'X'</span><span class="special">);</span>
 333 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">p</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
 334 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="identifier">make_pair</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;(</span><span class="char">'X'</span><span class="special">)</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
 335 <span class="identifier">assert</span><span class="special">((</span><span class="identifier">p</span> <span class="special">==</span> <span class="identifier">make_pair</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;(</span><span class="char">'X'</span><span class="special">)));</span>
 336 </pre>
 337 </div>
 338 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 339 <td align="left"></td>
 340 <td align="right"><div class="copyright-footer">Copyright &#169; 2001-2006, 2011, 2012 Joel de Guzman,
 341       Dan Marsden, Tobias Schwinger<p>
 342         Distributed under the Boost Software License, Version 1.0. (See accompanying
 343         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
 344       </p>
 345 </div></td>
 346 </tr></table>
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 348 <div class="spirit-nav">
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