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  26 <div class="titlepage"><div><div><h4 class="title">
  27 <a name="spirit_repository.qi_components.operators.keyword_list"></a><a class="link" href="keyword_list.html" title="Keyword List Operator">Keyword
  28         List Operator</a>
  29 </h4></div></div></div>
  30 <h6>
  31 <a name="spirit_repository.qi_components.operators.keyword_list.h0"></a>
  32           <span class="phrase"><a name="spirit_repository.qi_components.operators.keyword_list.description"></a></span><a class="link" href="keyword_list.html#spirit_repository.qi_components.operators.keyword_list.description">Description</a>
  33         </h6>
  34 <p>
  35           The keyword list operator, <code class="computeroutput"><span class="identifier">kwd</span><span class="special">(</span><span class="string">"k1"</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span>
  36           <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="string">"k2"</span><span class="special">)[</span><span class="identifier">b</span><span class="special">]</span></code>,
  37           works tightly with the kwd, ikwd, dkwd and idkwd directives to effeciently
  38           match keyword lists. As long as one of the keywords specified through the
  39           kwd, ikwd, dkwd or idkwd directive matches, the keyword will be immediatly
  40           followed by the keyword's associated subject parser. The parser will continue
  41           parsing input as long as the one of the keywords and it's associated parser
  42           succeed. Writing : (kwd("k1")[a] / kwd("k2")[b] / ...
  43           ) is equivalent to: *( "k1" &gt; a | "k2" &gt; b ...
  44           ).
  45         </p>
  46 <h6>
  47 <a name="spirit_repository.qi_components.operators.keyword_list.h1"></a>
  48           <span class="phrase"><a name="spirit_repository.qi_components.operators.keyword_list.header"></a></span><a class="link" href="keyword_list.html#spirit_repository.qi_components.operators.keyword_list.header">Header</a>
  49         </h6>
  50 <pre class="programlisting"><span class="comment">// forwards to &lt;boost/spirit/repository/home/qi/operator/keywords.hpp&gt;</span>
  51 <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">repository</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">qi_keywords</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
  52 </pre>
  53 <h6>
  54 <a name="spirit_repository.qi_components.operators.keyword_list.h2"></a>
  55           <span class="phrase"><a name="spirit_repository.qi_components.operators.keyword_list.expression_semantics"></a></span><a class="link" href="keyword_list.html#spirit_repository.qi_components.operators.keyword_list.expression_semantics">Expression
  56           Semantics</a>
  57         </h6>
  58 <div class="informaltable"><table class="table">
  59 <colgroup>
  60 <col>
  61 <col>
  62 </colgroup>
  63 <thead><tr>
  64 <th>
  65                   <p>
  66                     Expression
  67                   </p>
  68                 </th>
  69 <th>
  70                   <p>
  71                     Semantics
  72                   </p>
  73                 </th>
  74 </tr></thead>
  75 <tbody><tr>
  76 <td>
  77                   <p>
  78                     <code class="computeroutput"><span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k1</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span>
  79                     <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k2</span><span class="special">)[</span><span class="identifier">b</span><span class="special">]</span></code>
  80                   </p>
  81                 </td>
  82 <td>
  83                   <p>
  84                     Match <code class="computeroutput"><span class="identifier">lit</span><span class="special">(</span><span class="identifier">k1</span><span class="special">)</span>
  85                     <span class="special">&gt;</span> <span class="identifier">a</span></code>
  86                     or <code class="computeroutput"><span class="identifier">lit</span><span class="special">(</span><span class="identifier">k2</span><span class="special">)</span>
  87                     <span class="special">&gt;</span> <span class="identifier">b</span></code>,
  88                     equivalent to <code class="computeroutput"><span class="identifier">lit</span><span class="special">(</span><span class="identifier">k1</span><span class="special">)</span> <span class="special">&gt;</span>
  89                     <span class="identifier">a</span> <span class="special">|</span>
  90                     <span class="identifier">lit</span><span class="special">(</span><span class="identifier">k2</span><span class="special">)</span>
  91                     <span class="special">&gt;</span> <span class="identifier">b</span></code>
  92                   </p>
  93                 </td>
  94 </tr></tbody>
  95 </table></div>
  96 <h6>
  97 <a name="spirit_repository.qi_components.operators.keyword_list.h3"></a>
  98           <span class="phrase"><a name="spirit_repository.qi_components.operators.keyword_list.attributes"></a></span><a class="link" href="keyword_list.html#spirit_repository.qi_components.operators.keyword_list.attributes">Attributes</a>
  99         </h6>
 100 <div class="informaltable"><table class="table">
 101 <colgroup>
 102 <col>
 103 <col>
 104 </colgroup>
 105 <thead><tr>
 106 <th>
 107                   <p>
 108                     Expression
 109                   </p>
 110                 </th>
 111 <th>
 112                   <p>
 113                     Attribute
 114                   </p>
 115                 </th>
 116 </tr></thead>
 117 <tbody><tr>
 118 <td>
 119                   <p>
 120                     <code class="computeroutput"><span class="identifier">kwd</span><span class="special">(</span><span class="string">"k1"</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span>
 121                     <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="string">"k2"</span><span class="special">)[</span><span class="identifier">b</span><span class="special">]</span></code>
 122                   </p>
 123                 </td>
 124 <td>
 125                   <p>
 126 </p>
 127 <pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">a</span><span class="special">:</span> <span class="identifier">A</span><span class="special">,</span> <span class="identifier">b</span><span class="special">:</span> <span class="identifier">B</span> <span class="special">--&gt;</span> <span class="special">(</span><span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k1</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span> <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k2</span><span class="special">)[</span><span class="identifier">b</span><span class="special">]):</span> <span class="identifier">tuple</span><span class="special">&lt;</span><span class="identifier">A</span><span class="special">,</span> <span class="identifier">B</span><span class="special">&gt;</span>
 128 <span class="identifier">a</span><span class="special">:</span> <span class="identifier">A</span><span class="special">,</span> <span class="identifier">b</span><span class="special">:</span> <span class="identifier">Unused</span> <span class="special">--&gt;</span> <span class="special">(</span><span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k1</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span> <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k2</span><span class="special">)[</span><span class="identifier">b</span><span class="special">]):</span> <span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">A</span><span class="special">&gt;</span>
 129 <span class="identifier">a</span><span class="special">:</span> <span class="identifier">Unused</span><span class="special">,</span> <span class="identifier">b</span><span class="special">:</span> <span class="identifier">B</span> <span class="special">--&gt;</span> <span class="special">(</span><span class="identifier">kwd</span><span class="special">(</span><span class="string">"k1"</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span> <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k2</span><span class="special">)[</span><span class="identifier">b</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>
 130 <span class="identifier">a</span><span class="special">:</span> <span class="identifier">Unused</span><span class="special">,</span> <span class="identifier">b</span><span class="special">:</span> <span class="identifier">Unused</span> <span class="special">--&gt;</span> <span class="special">(</span><span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k1</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span> <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k2</span><span class="special">)[</span><span class="identifier">b</span><span class="special">]):</span> <span class="identifier">Unused</span>
 131
 132 <span class="identifier">a</span><span class="special">:</span> <span class="identifier">A</span><span class="special">,</span> <span class="identifier">b</span><span class="special">:</span> <span class="identifier">A</span> <span class="special">--&gt;(</span><span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k1</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]</span> <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="identifier">k2</span><span class="special">)[</span><span class="identifier">b</span><span class="special">]):</span> <span class="identifier">tuple</span><span class="special">&lt;</span><span class="identifier">A</span><span class="special">,</span> <span class="identifier">A</span><span class="special">&gt;</span></pre>
 133 <p>
 134                   </p>
 135                 </td>
 136 </tr></tbody>
 137 </table></div>
 138 <div class="note"><table border="0" summary="Note">
 139 <tr>
 140 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../images/note.png"></td>
 141 <th align="left">Note</th>
 142 </tr>
 143 <tr><td align="left" valign="top"><p>
 144             The keyword list parser works tightly with the kwd, ikwd, dkwd and idkwd
 145             directives and can't be used without it. A compile time error will warn
 146             you of any mistakes. This parser collects all the kwd directives and
 147             extracts the keyword literals or parsers from the directives to internaly
 148             build a Ternary Search Tree (TST) and permutation loop (for complex parsers)
 149             to effectively parse the keywords. Because you can't mix character types
 150             inside a TST you must take care not to mix wide strings with normal strings
 151             in the keywords you supply to a keyword list. Should it happen the compiler
 152             will trap the mistake for you.
 153           </p></td></tr>
 154 </table></div>
 155 <div class="note"><table border="0" summary="Note">
 156 <tr>
 157 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../images/note.png"></td>
 158 <th align="left">Note</th>
 159 </tr>
 160 <tr><td align="left" valign="top"><p>
 161             The kwd directive also works a bit like the repeat directive and can
 162             be used to formulate additional contraints on the number of times a keyword
 163             can or must occur while parsing a keyword list.
 164           </p></td></tr>
 165 </table></div>
 166 <div class="note"><table border="0" summary="Note">
 167 <tr>
 168 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../images/note.png"></td>
 169 <th align="left">Note</th>
 170 </tr>
 171 <tr><td align="left" valign="top"><p>
 172             The kwd, dkwd and ikwd, idkwd directives can be mixed inside a keyword
 173             list. This has however a small overhead and should be avoided when possible.
 174           </p></td></tr>
 175 </table></div>
 176 <h6>
 177 <a name="spirit_repository.qi_components.operators.keyword_list.h4"></a>
 178           <span class="phrase"><a name="spirit_repository.qi_components.operators.keyword_list.complexity"></a></span><a class="link" href="keyword_list.html#spirit_repository.qi_components.operators.keyword_list.complexity">Complexity</a>
 179         </h6>
 180 <div class="blockquote"><blockquote class="blockquote"><p>
 181             The overall complexity of the keyword list parser is defined by the sum
 182             of the complexities of its elements.
 183           </p></blockquote></div>
 184 <h6>
 185 <a name="spirit_repository.qi_components.operators.keyword_list.h5"></a>
 186           <span class="phrase"><a name="spirit_repository.qi_components.operators.keyword_list.example"></a></span><a class="link" href="keyword_list.html#spirit_repository.qi_components.operators.keyword_list.example">Example</a>
 187         </h6>
 188 <div class="note"><table border="0" summary="Note">
 189 <tr>
 190 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../images/note.png"></td>
 191 <th align="left">Note</th>
 192 </tr>
 193 <tr><td align="left" valign="top"><p>
 194             The test harness for the example(s) below is presented in the <a href="../../../../../../doc/html/spirit/qi/reference/basics.html#spirit.qi.reference.basics.examples" target="_top">Basics
 195             Examples</a> section.
 196           </p></td></tr>
 197 </table></div>
 198 <p>
 199           Declare a small data structure representing a person:
 200         </p>
 201 <p>
 202 </p>
 203 <pre class="programlisting"><span class="comment">// Data structure definitions to test the kwd directive</span>
 204 <span class="comment">// and the keywords list operator</span>
 205
 206 <span class="keyword">struct</span> <span class="identifier">person</span> <span class="special">{</span>
 207     <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">name</span><span class="special">;</span>
 208     <span class="keyword">int</span> <span class="identifier">age</span><span class="special">;</span>
 209     <span class="keyword">double</span> <span class="identifier">size</span><span class="special">;</span>
 210     <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&gt;</span> <span class="identifier">favorite_colors</span><span class="special">;</span>
 211
 212 <span class="special">};</span>
 213
 214 <span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span> <span class="special">&amp;</span><span class="keyword">operator</span><span class="special">&lt;&lt;(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span> <span class="special">&amp;</span><span class="identifier">os</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">person</span> <span class="special">&amp;</span><span class="identifier">p</span><span class="special">)</span>
 215 <span class="special">{</span>
 216     <span class="identifier">os</span><span class="special">&lt;&lt;</span><span class="string">"Person : "</span><span class="special">&lt;&lt;</span><span class="identifier">p</span><span class="special">.</span><span class="identifier">name</span><span class="special">&lt;&lt;</span><span class="string">", "</span><span class="special">&lt;&lt;</span><span class="identifier">p</span><span class="special">.</span><span class="identifier">age</span><span class="special">&lt;&lt;</span><span class="string">", "</span><span class="special">&lt;&lt;</span><span class="identifier">p</span><span class="special">.</span><span class="identifier">size</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>
 217     <span class="identifier">std</span><span class="special">::</span><span class="identifier">copy</span><span class="special">(</span><span class="identifier">p</span><span class="special">.</span><span class="identifier">favorite_colors</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span><span class="identifier">p</span><span class="special">.</span><span class="identifier">favorite_colors</span><span class="special">.</span><span class="identifier">end</span><span class="special">(),</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream_iterator</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&gt;(</span><span class="identifier">os</span><span class="special">,</span><span class="string">"\n"</span><span class="special">));</span>
 218     <span class="keyword">return</span> <span class="identifier">os</span><span class="special">;</span>
 219 <span class="special">}</span>
 220
 221 <span class="identifier">BOOST_FUSION_ADAPT_STRUCT</span><span class="special">(</span> <span class="identifier">person</span><span class="special">,</span>
 222     <span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">,</span> <span class="identifier">name</span><span class="special">)</span>
 223     <span class="special">(</span><span class="keyword">int</span><span class="special">,</span> <span class="identifier">age</span><span class="special">)</span>
 224     <span class="special">(</span><span class="keyword">double</span><span class="special">,</span> <span class="identifier">size</span><span class="special">)</span>
 225     <span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&gt;,</span> <span class="identifier">favorite_colors</span><span class="special">)</span>
 226 <span class="special">)</span>
 227 </pre>
 228 <p>
 229         </p>
 230 <p>
 231           Some using declarations:
 232         </p>
 233 <p>
 234 </p>
 235 <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">repository</span><span class="special">::</span><span class="identifier">qi</span><span class="special">::</span><span class="identifier">kwd</span><span class="special">;</span>
 236 <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">qi</span><span class="special">::</span><span class="identifier">inf</span><span class="special">;</span>
 237 <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">ascii</span><span class="special">::</span><span class="identifier">space_type</span><span class="special">;</span>
 238 <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">ascii</span><span class="special">::</span><span class="identifier">char_</span><span class="special">;</span>
 239 <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">qi</span><span class="special">::</span><span class="identifier">double_</span><span class="special">;</span>
 240 <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">qi</span><span class="special">::</span><span class="identifier">int_</span><span class="special">;</span>
 241 <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">qi</span><span class="special">::</span><span class="identifier">rule</span><span class="special">;</span>
 242 </pre>
 243 <p>
 244         </p>
 245 <p>
 246           Now let's declare a keyword parser:
 247         </p>
 248 <p>
 249 </p>
 250 <pre class="programlisting"><span class="identifier">no_constraint_person_rule</span> <span class="special">%=</span>
 251     <span class="identifier">kwd</span><span class="special">(</span><span class="string">"name"</span><span class="special">)[</span><span class="char">'='</span> <span class="special">&gt;</span> <span class="identifier">parse_string</span> <span class="special">]</span>
 252   <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="string">"age"</span><span class="special">)</span>   <span class="special">[</span><span class="char">'='</span> <span class="special">&gt;</span> <span class="identifier">int_</span><span class="special">]</span>
 253   <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="string">"size"</span><span class="special">)</span>   <span class="special">[</span><span class="char">'='</span> <span class="special">&gt;</span> <span class="identifier">double_</span> <span class="special">&gt;</span> <span class="char">'m'</span><span class="special">]</span>
 254   <span class="special">;</span>
 255 </pre>
 256 <p>
 257         </p>
 258 <p>
 259           A couple of input string variations run on the same parser:
 260         </p>
 261 <p>
 262           Parsing a keyword list:
 263         </p>
 264 <p>
 265 </p>
 266 <pre class="programlisting"><span class="comment">// Let's declare a small list of people for which we want to collect information.</span>
 267 <span class="identifier">person</span> <span class="identifier">John</span><span class="special">,</span><span class="identifier">Mary</span><span class="special">,</span><span class="identifier">Mike</span><span class="special">,</span><span class="identifier">Hellen</span><span class="special">,</span><span class="identifier">Johny</span><span class="special">;</span>
 268 <span class="identifier">test_phrase_parser_attr</span><span class="special">(</span>
 269                 <span class="string">"name = \"John\" \n age = 10 \n size = 1.69m "</span>
 270                 <span class="special">,</span><span class="identifier">no_constraint_person_rule</span>
 271                 <span class="special">,</span><span class="identifier">John</span><span class="special">);</span>  <span class="comment">// full in orginal order</span>
 272 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span><span class="special">&lt;&lt;</span><span class="identifier">John</span><span class="special">;</span>
 273
 274 <span class="identifier">test_phrase_parser_attr</span><span class="special">(</span>
 275                 <span class="string">"age = 10 \n size = 1.69m \n name = \"Mary\""</span>
 276                 <span class="special">,</span><span class="identifier">no_constraint_person_rule</span>
 277                 <span class="special">,</span><span class="identifier">Mary</span><span class="special">);</span>  <span class="comment">// keyword oder doesn't matter</span>
 278 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span><span class="special">&lt;&lt;</span><span class="identifier">Mary</span><span class="special">;</span>
 279
 280 <span class="identifier">test_phrase_parser_attr</span><span class="special">(</span>
 281                  <span class="string">"size = 1.69m \n name = \"Mike\" \n age = 10 "</span>
 282                 <span class="special">,</span><span class="identifier">no_constraint_person_rule</span>
 283                 <span class="special">,</span><span class="identifier">Mike</span><span class="special">);</span>  <span class="comment">// still the same result</span>
 284
 285 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span><span class="special">&lt;&lt;</span><span class="identifier">Mike</span><span class="special">;</span>
 286 </pre>
 287 <p>
 288         </p>
 289 <p>
 290           The code above will print:
 291         </p>
 292 <pre class="programlisting">Person : John, 10, 1.69
 293 Person : Mary, 10, 1.69
 294 Person : Mike, 10, 1.69
 295 </pre>
 296 <p>
 297           Now let's delcare a parser with some occurence constraints:
 298         </p>
 299 <p>
 300           The parser definition below uses the kwd directive occurence constraint
 301           variants to make sure that the name and age keyword occur only once and
 302           allows the favorite color entry to appear 0 or more times.
 303         </p>
 304 <p>
 305 </p>
 306 <pre class="programlisting"><span class="identifier">constraint_person_rule</span> <span class="special">%=</span>
 307     <span class="identifier">kwd</span><span class="special">(</span><span class="string">"name"</span><span class="special">,</span><span class="number">1</span><span class="special">)</span>                 <span class="special">[</span><span class="char">'='</span> <span class="special">&gt;</span> <span class="identifier">parse_string</span> <span class="special">]</span>
 308   <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="string">"age"</span>   <span class="special">,</span><span class="number">1</span><span class="special">)</span>                 <span class="special">[</span><span class="char">'='</span> <span class="special">&gt;</span> <span class="identifier">int_</span><span class="special">]</span>
 309   <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="string">"size"</span>   <span class="special">,</span><span class="number">1</span><span class="special">)</span>                 <span class="special">[</span><span class="char">'='</span> <span class="special">&gt;</span> <span class="identifier">double_</span> <span class="special">&gt;</span> <span class="char">'m'</span><span class="special">]</span>
 310   <span class="special">/</span> <span class="identifier">kwd</span><span class="special">(</span><span class="string">"favorite color"</span><span class="special">,</span><span class="number">0</span><span class="special">,</span><span class="identifier">inf</span><span class="special">)</span> <span class="special">[</span> <span class="char">'='</span> <span class="special">&gt;</span> <span class="identifier">parse_string</span> <span class="special">]</span>
 311   <span class="special">;</span>
 312 </pre>
 313 <p>
 314         </p>
 315 <p>
 316           And see how it works in these two cases:
 317         </p>
 318 <p>
 319 </p>
 320 <pre class="programlisting"> <span class="comment">// Here all the give constraint are resepected : parsing will succeed.</span>
 321  <span class="identifier">test_phrase_parser_attr</span><span class="special">(</span>
 322      <span class="string">"name = \"Hellen\" \n age = 10 \n size = 1.80m \n favorite color = \"blue\" \n favorite color = \"green\" "</span>
 323      <span class="special">,</span><span class="identifier">constraint_person_rule</span>
 324      <span class="special">,</span><span class="identifier">Hellen</span><span class="special">);</span>
 325  <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span><span class="special">&lt;&lt;</span><span class="identifier">Hellen</span><span class="special">;</span>
 326
 327 <span class="comment">// Parsing this string will fail because the age and size minimum occurence requirements aren't met.</span>
 328 <span class="identifier">test_phrase_parser_attr</span><span class="special">(</span>
 329      <span class="string">"name = \"Johny\"  \n favorite color = \"blue\" \n favorite color = \"green\" "</span>
 330      <span class="special">,</span><span class="identifier">constraint_person_rule</span>
 331      <span class="special">,</span><span class="identifier">Johny</span> <span class="special">);</span>
 332 </pre>
 333 <p>
 334         </p>
 335 <p>
 336           Parsing the first string will succeed but fail for the second string as
 337           the occurence constraints aren't met. This code should print:
 338         </p>
 339 <pre class="programlisting">Person : Hellen, 10, 1.8
 340 blue
 341 green
 342 </pre>
 343 </div>
 344 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 345 <td align="left"></td>
 346 <td align="right"><div class="copyright-footer">Copyright &#169; 2001-2011 Joel de Guzman, Hartmut Kaiser<p>
 347         Distributed under the Boost Software License, Version 1.0. (See accompanying
 348         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>)
 349       </p>
 350 </div></td>
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