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  25 <div class="section">
  26 <div class="titlepage"><div><div><h5 class="title">
  27 <a name="spirit.karma.reference.numeric.boolean"></a><a class="link" href="boolean.html" title="Boolean Generators (bool_)">Boolean Generators
  28           (<code class="computeroutput"><span class="identifier">bool_</span></code>)</a>
  29 </h5></div></div></div>
  30 <h6>
  31 <a name="spirit.karma.reference.numeric.boolean.h0"></a>
  32             <span class="phrase"><a name="spirit.karma.reference.numeric.boolean.description"></a></span><a class="link" href="boolean.html#spirit.karma.reference.numeric.boolean.description">Description</a>
  33           </h6>
  34 <p>
  35             As you might expect, the <code class="computeroutput"><span class="identifier">bool_generator</span></code>
  36             can generate output from boolean values. The <code class="computeroutput"><span class="identifier">bool_generator</span></code>
  37             generator can be used to generate output from ordinary primitive C/C++
  38             <code class="computeroutput"><span class="keyword">bool</span></code> values or user defined
  39             boolean types if the type follows certain expression requirements (for
  40             more information about the requirements, see <a class="link" href="boolean.html#spirit.karma.reference.numeric.boolean.additional_requirements">below</a>)).
  41             The <code class="computeroutput"><span class="identifier">bool_generator</span></code> is
  42             a template class. Template parameters fine tune its behavior.
  43           </p>
  44 <h6>
  45 <a name="spirit.karma.reference.numeric.boolean.h1"></a>
  46             <span class="phrase"><a name="spirit.karma.reference.numeric.boolean.header"></a></span><a class="link" href="boolean.html#spirit.karma.reference.numeric.boolean.header">Header</a>
  47           </h6>
  48 <pre class="programlisting"><span class="comment">// forwards to &lt;boost/spirit/home/karma/numeric/bool.hpp&gt;</span>
  49 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">spirit</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">karma_bool</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
  50 </pre>
  51 <p>
  52             Also, see <a class="link" href="../../../structure/include.html" title="Include">Include Structure</a>.
  53           </p>
  54 <h6>
  55 <a name="spirit.karma.reference.numeric.boolean.h2"></a>
  56             <span class="phrase"><a name="spirit.karma.reference.numeric.boolean.namespace"></a></span><a class="link" href="boolean.html#spirit.karma.reference.numeric.boolean.namespace">Namespace</a>
  57           </h6>
  58 <div class="informaltable"><table class="table">
  59 <colgroup><col></colgroup>
  60 <thead><tr><th>
  61                     <p>
  62                       Name
  63                     </p>
  64                   </th></tr></thead>
  65 <tbody>
  66 <tr><td>
  67                     <p>
  68                       <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">lit</span> <span class="comment">// alias:
  69                       boost::spirit::karma::lit</span></code>
  70                     </p>
  71                   </td></tr>
  72 <tr><td>
  73                     <p>
  74                       <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">bool_</span> <span class="comment">//
  75                       alias: boost::spirit::karma::bool_</span></code>
  76                     </p>
  77                   </td></tr>
  78 <tr><td>
  79                     <p>
  80                       <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">true_</span> <span class="comment">//
  81                       alias: boost::spirit::karma::true_</span></code>
  82                     </p>
  83                   </td></tr>
  84 <tr><td>
  85                     <p>
  86                       <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">false_</span> <span class="comment">//
  87                       alias: boost::spirit::karma::false_</span></code>
  88                     </p>
  89                   </td></tr>
  90 </tbody>
  91 </table></div>
  92 <div class="note"><table border="0" summary="Note">
  93 <tr>
  94 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../images/note.png"></td>
  95 <th align="left">Note</th>
  96 </tr>
  97 <tr><td align="left" valign="top"><p>
  98               <code class="computeroutput"><span class="identifier">lit</span></code> is reused by the
  99               <a class="link" href="../string.html" title="String Generators">String Generators</a>,
 100               the <a class="link" href="../char.html" title="Char Generators">Character Generators</a>,
 101               and the Numeric Generators. In general, a char generator is created
 102               when you pass in a character, a string generator is created when you
 103               pass in a string, and a numeric generator is created when you use a
 104               numeric (boolean) literal.
 105             </p></td></tr>
 106 </table></div>
 107 <h6>
 108 <a name="spirit.karma.reference.numeric.boolean.h3"></a>
 109             <span class="phrase"><a name="spirit.karma.reference.numeric.boolean.synopsis"></a></span><a class="link" href="boolean.html#spirit.karma.reference.numeric.boolean.synopsis">Synopsis</a>
 110           </h6>
 111 <pre class="programlisting"><span class="keyword">template</span> <span class="special">&lt;</span>
 112     <span class="keyword">typename</span> <span class="identifier">B</span>
 113   <span class="special">,</span> <span class="keyword">unsigned</span> <span class="identifier">Policies</span><span class="special">&gt;</span>
 114 <span class="keyword">struct</span> <span class="identifier">bool_generator</span><span class="special">;</span>
 115 </pre>
 116 <h6>
 117 <a name="spirit.karma.reference.numeric.boolean.h4"></a>
 118             <span class="phrase"><a name="spirit.karma.reference.numeric.boolean.template_parameters"></a></span><a class="link" href="boolean.html#spirit.karma.reference.numeric.boolean.template_parameters">Template
 119             parameters</a>
 120           </h6>
 121 <div class="informaltable"><table class="table">
 122 <colgroup>
 123 <col>
 124 <col>
 125 <col>
 126 </colgroup>
 127 <thead><tr>
 128 <th>
 129                     <p>
 130                       Parameter
 131                     </p>
 132                   </th>
 133 <th>
 134                     <p>
 135                       Description
 136                     </p>
 137                   </th>
 138 <th>
 139                     <p>
 140                       Default
 141                     </p>
 142                   </th>
 143 </tr></thead>
 144 <tbody>
 145 <tr>
 146 <td>
 147                     <p>
 148                       <code class="computeroutput"><span class="identifier">B</span></code>
 149                     </p>
 150                   </td>
 151 <td>
 152                     <p>
 153                       The boolean base type of the boolean generator.
 154                     </p>
 155                   </td>
 156 <td>
 157                     <p>
 158                       <code class="computeroutput"><span class="keyword">bool</span></code>
 159                     </p>
 160                   </td>
 161 </tr>
 162 <tr>
 163 <td>
 164                     <p>
 165                       <code class="computeroutput"><span class="identifier">Policies</span></code>
 166                     </p>
 167                   </td>
 168 <td>
 169                     <p>
 170                       The policies to use while converting the boolean.
 171                     </p>
 172                   </td>
 173 <td>
 174                     <p>
 175                       <code class="computeroutput"><span class="identifier">bool_policies</span><span class="special">&lt;</span><span class="identifier">B</span><span class="special">&gt;</span></code>
 176                     </p>
 177                   </td>
 178 </tr>
 179 </tbody>
 180 </table></div>
 181 <h6>
 182 <a name="spirit.karma.reference.numeric.boolean.h5"></a>
 183             <span class="phrase"><a name="spirit.karma.reference.numeric.boolean.model_of"></a></span><a class="link" href="boolean.html#spirit.karma.reference.numeric.boolean.model_of">Model
 184             of</a>
 185           </h6>
 186 <div class="blockquote"><blockquote class="blockquote"><p>
 187               <a class="link" href="../generator_concepts/primitivegenerator.html" title="PrimitiveGenerator"><code class="computeroutput"><span class="identifier">PrimitiveGenerator</span></code></a>
 188             </p></blockquote></div>
 189 <div class="variablelist">
 190 <p class="title"><b>Notation</b></p>
 191 <dl class="variablelist">
 192 <dt><span class="term"><code class="computeroutput"><span class="identifier">b</span></code></span></dt>
 193 <dd><p>
 194                   Boolean literal, or a <a class="link" href="../basics.html#spirit.karma.reference.basics.lazy_argument">Lazy
 195                   Argument</a> that evaluates to a boolean value of type <code class="computeroutput"><span class="identifier">B</span></code>
 196                 </p></dd>
 197 <dt><span class="term"><code class="computeroutput"><span class="identifier">B</span></code></span></dt>
 198 <dd><p>
 199                   Type of <code class="computeroutput"><span class="identifier">b</span></code>: any
 200                   type usable as a boolean, or in case of a <a class="link" href="../basics.html#spirit.karma.reference.basics.lazy_argument">Lazy
 201                   Argument</a>, its return value
 202                 </p></dd>
 203 </dl>
 204 </div>
 205 <h6>
 206 <a name="spirit.karma.reference.numeric.boolean.h6"></a>
 207             <span class="phrase"><a name="spirit.karma.reference.numeric.boolean.expression_semantics"></a></span><a class="link" href="boolean.html#spirit.karma.reference.numeric.boolean.expression_semantics">Expression
 208             Semantics</a>
 209           </h6>
 210 <p>
 211             Semantics of an expression is defined only where it differs from, or
 212             is not defined in <a class="link" href="../generator_concepts/primitivegenerator.html" title="PrimitiveGenerator"><code class="computeroutput"><span class="identifier">PrimitiveGenerator</span></code></a>.
 213           </p>
 214 <div class="informaltable"><table class="table">
 215 <colgroup>
 216 <col>
 217 <col>
 218 </colgroup>
 219 <thead><tr>
 220 <th>
 221                     <p>
 222                       Expression
 223                     </p>
 224                   </th>
 225 <th>
 226                     <p>
 227                       Semantics
 228                     </p>
 229                   </th>
 230 </tr></thead>
 231 <tbody>
 232 <tr>
 233 <td>
 234                     <p>
 235                       <code class="computeroutput"><span class="identifier">lit</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>
 236                     </p>
 237                   </td>
 238 <td>
 239                     <p>
 240                       Generate the boolean literal <code class="computeroutput"><span class="identifier">b</span></code>
 241                       using the default formatting (<code class="computeroutput"><span class="keyword">false</span></code>
 242                       is generated as <code class="computeroutput"><span class="string">"false"</span></code>,
 243                       and <code class="computeroutput"><span class="keyword">true</span></code> is generated
 244                       as <code class="computeroutput"><span class="string">"true"</span></code>).
 245                       This generator never fails (unless the underlying output stream
 246                       reports an error).
 247                     </p>
 248                   </td>
 249 </tr>
 250 <tr>
 251 <td>
 252                     <p>
 253                       <code class="computeroutput"><span class="identifier">bool_</span></code>
 254                     </p>
 255                   </td>
 256 <td>
 257                     <p>
 258                       Generate the boolean value provided by a mandatory attribute
 259                       using the default formatting (<code class="computeroutput"><span class="keyword">false</span></code>
 260                       is generated as <code class="computeroutput"><span class="string">"false"</span></code>,
 261                       and <code class="computeroutput"><span class="keyword">true</span></code> is generated
 262                       as <code class="computeroutput"><span class="string">"true"</span></code>).
 263                       This generator never fails (unless the underlying output stream
 264                       reports an error).
 265                     </p>
 266                   </td>
 267 </tr>
 268 <tr>
 269 <td>
 270                     <p>
 271                       <code class="computeroutput"><span class="identifier">bool_</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>
 272                     </p>
 273                   </td>
 274 <td>
 275                     <p>
 276                       Generate the boolean value provided by the immediate literal
 277                       value the generator is initialized from using the default formatting
 278                       (<code class="computeroutput"><span class="keyword">false</span></code> is generated
 279                       as <code class="computeroutput"><span class="string">"false"</span></code>,
 280                       and <code class="computeroutput"><span class="keyword">true</span></code> is generated
 281                       as <code class="computeroutput"><span class="string">"true"</span></code>).
 282                       If this generator has an associated attribute it succeeds only
 283                       if the attribute is equal to the immediate literal (unless
 284                       the underlying output stream reports an error). Otherwise this
 285                       generator fails and does not generate any output.
 286                     </p>
 287                   </td>
 288 </tr>
 289 <tr>
 290 <td>
 291                     <p>
 292                       <code class="computeroutput"><span class="identifier">true_</span></code>
 293                     </p>
 294                   </td>
 295 <td>
 296                     <p>
 297                       Generate <code class="computeroutput"><span class="string">"true"</span></code>.
 298                       If this generator has an associated attribute it succeeds only
 299                       if the attribute is <code class="computeroutput"><span class="keyword">true</span></code>
 300                       as well (unless the underlying output stream reports an error).
 301                     </p>
 302                   </td>
 303 </tr>
 304 <tr>
 305 <td>
 306                     <p>
 307                       <code class="computeroutput"><span class="identifier">false_</span></code>
 308                     </p>
 309                   </td>
 310 <td>
 311                     <p>
 312                       Generate <code class="computeroutput"><span class="string">"false"</span></code>.
 313                       If this generator has an associated attribute it succeeds only
 314                       if the attribute is <code class="computeroutput"><span class="keyword">false</span></code>
 315                       as well (unless the underlying output stream reports an error).
 316                     </p>
 317                   </td>
 318 </tr>
 319 </tbody>
 320 </table></div>
 321 <p>
 322             All generators listed in the table above (except <code class="computeroutput"><span class="identifier">lit</span><span class="special">(</span><span class="identifier">num</span><span class="special">)</span></code>) are predefined specializations of the
 323             <code class="computeroutput"><span class="identifier">bool_generator</span><span class="special">&lt;</span><span class="identifier">B</span><span class="special">,</span> <span class="identifier">Policies</span><span class="special">&gt;</span></code>
 324             basic boolean generator type described below. It is possible to directly
 325             use this type to create boolean generators using a wide range of formatting
 326             options.
 327           </p>
 328 <div class="informaltable"><table class="table">
 329 <colgroup>
 330 <col>
 331 <col>
 332 </colgroup>
 333 <thead><tr>
 334 <th>
 335                     <p>
 336                       Expression
 337                     </p>
 338                   </th>
 339 <th>
 340                     <p>
 341                       Semantics
 342                     </p>
 343                   </th>
 344 </tr></thead>
 345 <tbody>
 346 <tr>
 347 <td>
 348                     <p>
 349 </p>
 350 <pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">bool_generator</span><span class="special">&lt;</span>
 351     <span class="identifier">B</span><span class="special">,</span> <span class="identifier">Policies</span>
 352 <span class="special">&gt;()</span></pre>
 353 <p>
 354                     </p>
 355                   </td>
 356 <td>
 357                     <p>
 358                       Generate the boolean of type <code class="computeroutput"><span class="identifier">B</span></code>
 359                       provided by a mandatory attribute using the specified <code class="computeroutput"><span class="identifier">Policies</span></code> This generator never
 360                       fails (unless the underlying output stream reports an error).
 361                     </p>
 362                   </td>
 363 </tr>
 364 <tr>
 365 <td>
 366                     <p>
 367 </p>
 368 <pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">bool_generator</span><span class="special">&lt;</span>
 369     <span class="identifier">B</span><span class="special">,</span> <span class="identifier">Policies</span>
 370 <span class="special">&gt;()(</span><span class="identifier">b</span><span class="special">)</span></pre>
 371 <p>
 372                     </p>
 373                   </td>
 374 <td>
 375                     <p>
 376                       Generate the boolean of type <code class="computeroutput"><span class="identifier">B</span></code>
 377                       provided by the immediate literal value the generator is initialized
 378                       from, using the specified <code class="computeroutput"><span class="identifier">Policies</span></code>.
 379                       If this generator has an associated attribute it succeeds only
 380                       if the attribute is equal to the immediate literal (unless
 381                       the underlying output stream reports an error). Otherwise this
 382                       generator fails and does not generate any output.
 383                     </p>
 384                   </td>
 385 </tr>
 386 </tbody>
 387 </table></div>
 388 <div class="note"><table border="0" summary="Note">
 389 <tr>
 390 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../images/note.png"></td>
 391 <th align="left">Note</th>
 392 </tr>
 393 <tr><td align="left" valign="top"><p>
 394               All boolean generators properly respect the <a class="link" href="../directive/upperlower.html" title="Generator Directives Controlling Case Sensitivity (upper[], lower[])"><code class="computeroutput"><span class="identifier">upper</span></code></a> and <a class="link" href="../directive/upperlower.html" title="Generator Directives Controlling Case Sensitivity (upper[], lower[])"><code class="computeroutput"><span class="identifier">lower</span></code></a> directives.
 395             </p></td></tr>
 396 </table></div>
 397 <h6>
 398 <a name="spirit.karma.reference.numeric.boolean.h7"></a>
 399             <span class="phrase"><a name="spirit.karma.reference.numeric.boolean.additional_requirements"></a></span><a class="link" href="boolean.html#spirit.karma.reference.numeric.boolean.additional_requirements">Additional
 400             Requirements</a>
 401           </h6>
 402 <p>
 403             The following lists enumerate the requirements which must be met in order
 404             to use a certain type <code class="computeroutput"><span class="identifier">B</span></code>
 405             to instantiate and use a <code class="computeroutput"><span class="identifier">bool_generator</span><span class="special">&lt;</span><span class="identifier">B</span><span class="special">,</span> <span class="identifier">Policies</span><span class="special">&gt;</span></code>.
 406           </p>
 407 <p>
 408             The type <code class="computeroutput"><span class="identifier">B</span></code>:
 409           </p>
 410 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
 411                 must be (safely) convertible to <code class="computeroutput"><span class="keyword">bool</span></code>
 412               </li></ul></div>
 413 <h6>
 414 <a name="spirit.karma.reference.numeric.boolean.h8"></a>
 415             <span class="phrase"><a name="spirit.karma.reference.numeric.boolean.attributes"></a></span><a class="link" href="boolean.html#spirit.karma.reference.numeric.boolean.attributes">Attributes</a>
 416           </h6>
 417 <div class="informaltable"><table class="table">
 418 <colgroup>
 419 <col>
 420 <col>
 421 </colgroup>
 422 <thead><tr>
 423 <th>
 424                     <p>
 425                       Expression
 426                     </p>
 427                   </th>
 428 <th>
 429                     <p>
 430                       Attribute
 431                     </p>
 432                   </th>
 433 </tr></thead>
 434 <tbody>
 435 <tr>
 436 <td>
 437                     <p>
 438                       <code class="computeroutput"><span class="identifier">bool_</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>
 439                     </p>
 440                   </td>
 441 <td>
 442                     <p>
 443                       <code class="computeroutput"><span class="identifier">unused</span></code>
 444                     </p>
 445                   </td>
 446 </tr>
 447 <tr>
 448 <td>
 449                     <p>
 450                       <code class="computeroutput"><span class="identifier">bool_</span></code>
 451                     </p>
 452                   </td>
 453 <td>
 454                     <p>
 455                       <code class="computeroutput"><span class="keyword">bool</span></code>, attribute
 456                       is mandatory (otherwise compilation will fail)
 457                     </p>
 458                   </td>
 459 </tr>
 460 <tr>
 461 <td>
 462                     <p>
 463                       <code class="computeroutput"><span class="identifier">bool_</span><span class="special">(</span><span class="identifier">b</span><span class="special">)</span></code>
 464                     </p>
 465                   </td>
 466 <td>
 467                     <p>
 468                       <code class="computeroutput"><span class="keyword">bool</span></code>, attribute
 469                       is optional, if it is supplied, the generator compares the
 470                       attribute with <code class="computeroutput"><span class="identifier">b</span></code>
 471                       and succeeds only if both are equal, failing otherwise.
 472                     </p>
 473                   </td>
 474 </tr>
 475 <tr>
 476 <td>
 477                     <p>
 478 </p>
 479 <pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">bool_generator</span><span class="special">&lt;</span>
 480     <span class="identifier">B</span><span class="special">,</span> <span class="identifier">Policies</span>
 481 <span class="special">&gt;()</span></pre>
 482 <p>
 483                     </p>
 484                   </td>
 485 <td>
 486                     <p>
 487                       <code class="computeroutput"><span class="identifier">B</span></code>, attribute
 488                       is mandatory (otherwise compilation will fail)
 489                     </p>
 490                   </td>
 491 </tr>
 492 <tr>
 493 <td>
 494                     <p>
 495 </p>
 496 <pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">bool_generator</span><span class="special">&lt;</span>
 497     <span class="identifier">B</span><span class="special">,</span> <span class="identifier">Policies</span>
 498 <span class="special">&gt;()(</span><span class="identifier">b</span><span class="special">)</span></pre>
 499 <p>
 500                     </p>
 501                   </td>
 502 <td>
 503                     <p>
 504                       <code class="computeroutput"><span class="identifier">B</span></code>, attribute
 505                       is optional, if it is supplied, the generator compares the
 506                       attribute with <code class="computeroutput"><span class="identifier">b</span></code>
 507                       and succeeds only if both are equal, failing otherwise.
 508                     </p>
 509                   </td>
 510 </tr>
 511 </tbody>
 512 </table></div>
 513 <div class="note"><table border="0" summary="Note">
 514 <tr>
 515 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../images/note.png"></td>
 516 <th align="left">Note</th>
 517 </tr>
 518 <tr><td align="left" valign="top"><p>
 519               In addition to their usual attribute of type <code class="computeroutput"><span class="identifier">B</span></code>
 520               all listed generators accept an instance of a <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">B</span><span class="special">&gt;</span></code> as well. If the <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special">&lt;&gt;</span></code> is initialized (holds a value)
 521               the generators behave as if their attribute was an instance of <code class="computeroutput"><span class="identifier">B</span></code> and emit the value stored in the
 522               <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special">&lt;&gt;</span></code>.
 523               Otherwise the generators will fail.
 524             </p></td></tr>
 525 </table></div>
 526 <h6>
 527 <a name="spirit.karma.reference.numeric.boolean.h9"></a>
 528             <span class="phrase"><a name="spirit.karma.reference.numeric.boolean.boolean_formatting_policies"></a></span><a class="link" href="boolean.html#spirit.karma.reference.numeric.boolean.boolean_formatting_policies">Boolean
 529             Formatting Policies</a>
 530           </h6>
 531 <p>
 532             If special formatting of a boolean is needed, overload the policy class
 533             <code class="computeroutput"><span class="identifier">bool_policies</span><span class="special">&lt;</span><span class="identifier">B</span><span class="special">&gt;</span></code>
 534             and use it as a template parameter to the <code class="computeroutput"><span class="identifier">bool_generator</span><span class="special">&lt;&gt;</span></code> boolean generator. For instance:
 535           </p>
 536 <pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">special_bool_policy</span> <span class="special">:</span> <span class="identifier">karma</span><span class="special">::</span><span class="identifier">bool_policies</span><span class="special">&lt;&gt;</span>
 537 <span class="special">{</span>
 538     <span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">CharEncoding</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Tag</span>
 539       <span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">OutputIterator</span><span class="special">&gt;</span>
 540     <span class="keyword">static</span> <span class="keyword">bool</span> <span class="identifier">generate_false</span><span class="special">(</span><span class="identifier">OutputIterator</span><span class="special">&amp;</span> <span class="identifier">sink</span><span class="special">,</span> <span class="keyword">bool</span> <span class="identifier">b</span><span class="special">)</span>
 541     <span class="special">{</span>
 542         <span class="comment">// we want to spell the names of false as eurt (true backwards)</span>
 543         <span class="keyword">return</span> <span class="identifier">string_inserter</span><span class="special">&lt;</span><span class="identifier">CharEncoding</span><span class="special">,</span> <span class="identifier">Tag</span><span class="special">&gt;::</span><span class="identifier">call</span><span class="special">(</span><span class="identifier">sink</span><span class="special">,</span> <span class="string">"eurt"</span><span class="special">);</span>
 544     <span class="special">}</span>
 545 <span class="special">};</span>
 546
 547 <span class="keyword">typedef</span> <span class="identifier">karma</span><span class="special">::</span><span class="identifier">bool_generator</span><span class="special">&lt;</span><span class="identifier">special_bool_policy</span><span class="special">&gt;</span> <span class="identifier">backwards_bool_type</span><span class="special">;</span>
 548 <span class="identifier">backwards_bool_type</span> <span class="keyword">const</span> <span class="identifier">backwards_bool</span><span class="special">;</span>
 549
 550 <span class="identifier">karma</span><span class="special">::</span><span class="identifier">generate</span><span class="special">(</span><span class="identifier">sink</span><span class="special">,</span> <span class="identifier">backwards_bool</span><span class="special">,</span> <span class="keyword">true</span><span class="special">);</span>    <span class="comment">// will output: true</span>
 551 <span class="identifier">karma</span><span class="special">::</span><span class="identifier">generate</span><span class="special">(</span><span class="identifier">sink</span><span class="special">,</span> <span class="identifier">backwards_bool</span><span class="special">(</span><span class="keyword">false</span><span class="special">));</span>   <span class="comment">// will output: uert</span>
 552 </pre>
 553 <p>
 554             The template parameter <code class="computeroutput"><span class="identifier">B</span></code>
 555             should be the type to be formatted using the overloaded policy type.
 556             At the same time <code class="computeroutput"><span class="identifier">B</span></code> will
 557             be used as the attribute type of the created real number generator. The
 558             default for <code class="computeroutput"><span class="identifier">B</span></code> is <code class="computeroutput"><span class="keyword">bool</span></code>.
 559           </p>
 560 <h6>
 561 <a name="spirit.karma.reference.numeric.boolean.h10"></a>
 562             <span class="phrase"><a name="spirit.karma.reference.numeric.boolean.boolean_formatting_policy_expression_semantics"></a></span><a class="link" href="boolean.html#spirit.karma.reference.numeric.boolean.boolean_formatting_policy_expression_semantics">Boolean
 563             Formatting Policy Expression Semantics</a>
 564           </h6>
 565 <p>
 566             A boolean formatting policy should expose the following:
 567           </p>
 568 <div class="informaltable"><table class="table">
 569 <colgroup>
 570 <col>
 571 <col>
 572 </colgroup>
 573 <thead><tr>
 574 <th>
 575                     <p>
 576                       Expression
 577                     </p>
 578                   </th>
 579 <th>
 580                     <p>
 581                       Description
 582                     </p>
 583                   </th>
 584 </tr></thead>
 585 <tbody>
 586 <tr>
 587 <td>
 588                     <p>
 589 </p>
 590 <pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Inserter</span>
 591   <span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">OutputIterator</span>
 592   <span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Policies</span><span class="special">&gt;</span>
 593 <span class="keyword">bool</span> <span class="identifier">call</span> <span class="special">(</span><span class="identifier">OutputIterator</span><span class="special">&amp;</span> <span class="identifier">sink</span><span class="special">,</span> <span class="identifier">Num</span> <span class="identifier">n</span>
 594   <span class="special">,</span> <span class="identifier">Policies</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">p</span><span class="special">);</span>
 595 </pre>
 596 <p>
 597                     </p>
 598                   </td>
 599 <td>
 600                     <p>
 601                       This is the main function used to generate the output for a
 602                       boolean. It is called by the boolean generator in order to
 603                       perform the conversion. In theory all of the work can be implemented
 604                       here, but the easiest way is to use existing functionality
 605                       provided by the type specified by the template parameter <code class="computeroutput"><span class="identifier">Inserter</span></code>. The default implementation
 606                       of this functions is:
 607 </p>
 608 <pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Inserter</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">OutputIterator</span>
 609   <span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Policies</span><span class="special">&gt;</span>
 610 <span class="keyword">static</span> <span class="keyword">bool</span>
 611 <span class="identifier">call</span> <span class="special">(</span><span class="identifier">OutputIterator</span><span class="special">&amp;</span> <span class="identifier">sink</span><span class="special">,</span> <span class="identifier">B</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">Policies</span> <span class="keyword">const</span><span class="special">&amp;</span> <span class="identifier">p</span><span class="special">)</span>
 612 <span class="special">{</span>
 613     <span class="keyword">return</span> <span class="identifier">Inserter</span><span class="special">::</span><span class="identifier">call_n</span><span class="special">(</span><span class="identifier">sink</span><span class="special">,</span> <span class="identifier">b</span><span class="special">,</span> <span class="identifier">p</span><span class="special">);</span>
 614 <span class="special">}</span>
 615 </pre>
 616 <p>
 617                       <code class="computeroutput"><span class="identifier">sink</span></code> is the
 618                       output iterator to use for generation
 619                     </p>
 620                     <p>
 621                       <code class="computeroutput"><span class="identifier">b</span></code> is the boolean
 622                       to convert
 623                     </p>
 624                     <p>
 625                       <code class="computeroutput"><span class="identifier">p</span></code> is the instance
 626                       of the policy type used to instantiate this real number generator.
 627                     </p>
 628                   </td>
 629 </tr>
 630 <tr>
 631 <td>
 632                     <p>
 633 </p>
 634 <pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">CharEncoding</span><span class="special">,</span>
 635     <span class="keyword">typename</span> <span class="identifier">Tag</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">OutputIterator</span><span class="special">&gt;</span>
 636 <span class="keyword">bool</span> <span class="identifier">generate_false</span><span class="special">(</span>
 637     <span class="identifier">OutputIterator</span><span class="special">&amp;</span> <span class="identifier">sink</span><span class="special">,</span> <span class="identifier">B</span> <span class="identifier">b</span><span class="special">);</span>
 638 </pre>
 639 <p>
 640                     </p>
 641                   </td>
 642 <td>
 643                     <p>
 644                       This function is called to generate the boolean if it is <code class="computeroutput"><span class="keyword">false</span></code>.
 645                     </p>
 646                     <p>
 647                       <code class="computeroutput"><span class="identifier">sink</span></code> is the
 648                       output iterator to use for generation
 649                     </p>
 650                     <p>
 651                       <code class="computeroutput"><span class="identifier">b</span></code> is the boolean
 652                       to convert (the value is <code class="computeroutput"><span class="keyword">false</span></code>).
 653                     </p>
 654                     <p>
 655                       The template parameters <code class="computeroutput"><span class="identifier">CharEncoding</span></code>
 656                       and <code class="computeroutput"><span class="identifier">Tag</span></code> are
 657                       either of the type <code class="computeroutput"><span class="identifier">unused_type</span></code>
 658                       or describe the character class and conversion to be applied
 659                       to any output possibly influenced by either the <code class="computeroutput"><span class="identifier">lower</span><span class="special">[]</span></code>
 660                       or <code class="computeroutput"><span class="identifier">upper</span><span class="special">[]</span></code>
 661                       directives.
 662                     </p>
 663                     <p>
 664                       The return value defines the outcome of the whole generator.
 665                     </p>
 666                   </td>
 667 </tr>
 668 <tr>
 669 <td>
 670                     <p>
 671 </p>
 672 <pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">template</span> <span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">CharEncoding</span><span class="special">,</span>
 673     <span class="keyword">typename</span> <span class="identifier">Tag</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">OutputIterator</span><span class="special">&gt;</span>
 674 <span class="keyword">bool</span> <span class="identifier">generate_true</span><span class="special">(</span>
 675     <span class="identifier">OutputIterator</span><span class="special">&amp;</span> <span class="identifier">sink</span><span class="special">,</span> <span class="identifier">B</span> <span class="identifier">b</span><span class="special">);</span>
 676 </pre>
 677 <p>
 678                     </p>
 679                   </td>
 680 <td>
 681                     <p>
 682                       This function is called to generate the boolean if it is <code class="computeroutput"><span class="keyword">true</span></code>.
 683                     </p>
 684                     <p>
 685                       <code class="computeroutput"><span class="identifier">sink</span></code> is the
 686                       output iterator to use for generation
 687                     </p>
 688                     <p>
 689                       <code class="computeroutput"><span class="identifier">b</span></code> is the boolean
 690                       to convert (the value is <code class="computeroutput"><span class="keyword">true</span></code>).
 691                     </p>
 692                     <p>
 693                       The template parameters <code class="computeroutput"><span class="identifier">CharEncoding</span></code>
 694                       and <code class="computeroutput"><span class="identifier">Tag</span></code> are
 695                       either of the type <code class="computeroutput"><span class="identifier">unused_type</span></code>
 696                       or describe the character class and conversion to be applied
 697                       to any output possibly influenced by either the <code class="computeroutput"><span class="identifier">lower</span><span class="special">[]</span></code>
 698                       or <code class="computeroutput"><span class="identifier">upper</span><span class="special">[]</span></code>
 699                       directives.
 700                     </p>
 701                     <p>
 702                       The return value defines the outcome of the whole generator.
 703                     </p>
 704                   </td>
 705 </tr>
 706 </tbody>
 707 </table></div>
 708 <h6>
 709 <a name="spirit.karma.reference.numeric.boolean.h11"></a>
 710             <span class="phrase"><a name="spirit.karma.reference.numeric.boolean.complexity"></a></span><a class="link" href="boolean.html#spirit.karma.reference.numeric.boolean.complexity">Complexity</a>
 711           </h6>
 712 <div class="blockquote"><blockquote class="blockquote"><p>
 713               O(N), where <code class="computeroutput"><span class="identifier">N</span></code> is the
 714               number of characters needed to represent the generated boolean.
 715             </p></blockquote></div>
 716 <h6>
 717 <a name="spirit.karma.reference.numeric.boolean.h12"></a>
 718             <span class="phrase"><a name="spirit.karma.reference.numeric.boolean.example"></a></span><a class="link" href="boolean.html#spirit.karma.reference.numeric.boolean.example">Example</a>
 719           </h6>
 720 <div class="note"><table border="0" summary="Note">
 721 <tr>
 722 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../images/note.png"></td>
 723 <th align="left">Note</th>
 724 </tr>
 725 <tr><td align="left" valign="top"><p>
 726               The test harness for the example(s) below is presented in the <a class="link" href="../basics.html#spirit.karma.reference.basics.examples">Basics Examples</a>
 727               section.
 728             </p></td></tr>
 729 </table></div>
 730 <p>
 731             Some includes:
 732           </p>
 733 <p>
 734 </p>
 735 <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">spirit</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">karma</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 736 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">spirit</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">support_utree</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 737 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">spirit</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">phoenix_core</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 738 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">spirit</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">phoenix_operator</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 739 <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">std_pair</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 740 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>
 741 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">string</span><span class="special">&gt;</span>
 742 </pre>
 743 <p>
 744           </p>
 745 <p>
 746             Some using declarations:
 747           </p>
 748 <p>
 749 </p>
 750 <pre class="programlisting"><span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">karma</span><span class="special">::</span><span class="identifier">bool_</span><span class="special">;</span>
 751 <span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">karma</span><span class="special">::</span><span class="identifier">lit</span><span class="special">;</span>
 752 </pre>
 753 <p>
 754           </p>
 755 <p>
 756             Basic usage of an <code class="computeroutput"><span class="identifier">bool_</span></code>
 757             generator:
 758           </p>
 759 <p>
 760 </p>
 761 <pre class="programlisting"><span class="identifier">test_generator</span><span class="special">(</span><span class="string">"true"</span><span class="special">,</span> <span class="identifier">lit</span><span class="special">(</span><span class="keyword">true</span><span class="special">));</span>
 762 <span class="identifier">test_generator</span><span class="special">(</span><span class="string">"false"</span><span class="special">,</span> <span class="identifier">bool_</span><span class="special">(</span><span class="keyword">false</span><span class="special">));</span>
 763 <span class="identifier">test_generator_attr</span><span class="special">(</span><span class="string">"true"</span><span class="special">,</span> <span class="identifier">bool_</span><span class="special">(</span><span class="keyword">true</span><span class="special">),</span> <span class="keyword">true</span><span class="special">);</span>
 764 <span class="identifier">test_generator_attr</span><span class="special">(</span><span class="string">""</span><span class="special">,</span> <span class="identifier">bool_</span><span class="special">(</span><span class="keyword">true</span><span class="special">),</span> <span class="keyword">false</span><span class="special">);</span>    <span class="comment">// fails (as true != false)!</span>
 765 <span class="identifier">test_generator_attr</span><span class="special">(</span><span class="string">"false"</span><span class="special">,</span> <span class="identifier">bool_</span><span class="special">,</span> <span class="keyword">false</span><span class="special">);</span>
 766 </pre>
 767 <p>
 768           </p>
 769 </div>
 770 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 771 <td align="left"></td>
 772 <td align="right"><div class="copyright-footer">Copyright &#169; 2001-2011 Joel de Guzman, Hartmut Kaiser<p>
 773         Distributed under the Boost Software License, Version 1.0. (See accompanying
 774         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>)
 775       </p>
 776 </div></td>
 777 </tr></table>
 778 <hr>
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