1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Qi Distinct Parser Directive</title> 5<link rel="stylesheet" href="../../../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../../index.html" title="Spirit Repository 0.2"> 8<link rel="up" href="../directives.html" title="Qi Parser Directives"> 9<link rel="prev" href="confix.html" title="Qi Confix Parser Directive"> 10<link rel="next" href="kwd.html" title="Qi Keyword Parser Directive"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="confix.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../directives.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="kwd.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h4 class="title"> 27<a name="spirit_repository.qi_components.directives.distinct"></a><a class="link" href="distinct.html" title="Qi Distinct Parser Directive">Qi 28 Distinct Parser Directive</a> 29</h4></div></div></div> 30<h6> 31<a name="spirit_repository.qi_components.directives.distinct.h0"></a> 32 <span class="phrase"><a name="spirit_repository.qi_components.directives.distinct.description"></a></span><a class="link" href="distinct.html#spirit_repository.qi_components.directives.distinct.description">Description</a> 33 </h6> 34<p> 35 The <span class="emphasis"><em>Spirit.Qi</em></span> <code class="computeroutput"><span class="identifier">distinct</span></code> 36 parser is a directive component allowing to avoid partial matches while 37 parsing using a skipper. A simple example is the common task of matching 38 a C keyword. Consider: 39 </p> 40<pre class="programlisting"><span class="string">"description"</span> <span class="special">>></span> <span class="special">-</span><span class="identifier">lit</span><span class="special">(</span><span class="string">":"</span><span class="special">)</span> <span class="special">>></span> <span class="special">*(</span><span class="identifier">char_</span> <span class="special">-</span> <span class="identifier">eol</span><span class="special">)</span> 41</pre> 42<p> 43 intended to match a line in a configuration file. Let's assume further, 44 that this rule is used with a <code class="computeroutput"><span class="identifier">space</span></code> 45 skipper and that we have the following strings in the input: 46 </p> 47<pre class="programlisting"><span class="string">"description: ident\n"</span> 48<span class="string">"description ident\n"</span> 49<span class="string">"descriptionident\n"</span> 50</pre> 51<p> 52 It might seem unexpected, but the parser above matches all three inputs 53 just fine, even if the third input should not match at all! In order to 54 avoid the unwanted match we are forced to make our rule more complicated: 55 </p> 56<pre class="programlisting"><span class="identifier">lexeme</span><span class="special">[</span><span class="string">"description"</span> <span class="special">>></span> <span class="special">!</span><span class="identifier">char_</span><span class="special">(</span><span class="string">"a-zA-Z_0-9"</span><span class="special">)]</span> <span class="special">>></span> <span class="special">-</span><span class="identifier">lit</span><span class="special">(</span><span class="string">":"</span><span class="special">)</span> <span class="special">>></span> <span class="special">*(</span><span class="identifier">char_</span> <span class="special">-</span> <span class="identifier">eol</span><span class="special">)</span> 57</pre> 58<p> 59 (the rule reads as: match <code class="computeroutput"><span class="string">"description"</span></code> 60 as long as it's not <span class="emphasis"><em>directly</em></span> followed by a valid identifier). 61 </p> 62<p> 63 The <code class="computeroutput"><span class="identifier">distinct</span><span class="special">[]</span></code> 64 directive is meant to simplify the rule above: 65 </p> 66<pre class="programlisting"><span class="identifier">distinct</span><span class="special">(</span><span class="identifier">char_</span><span class="special">(</span><span class="string">"a-zA-Z_0-9"</span><span class="special">))[</span><span class="string">"description"</span><span class="special">]</span> <span class="special">>></span> <span class="special">-</span><span class="identifier">lit</span><span class="special">(</span><span class="string">":"</span><span class="special">)</span> <span class="special">>></span> <span class="special">*(</span><span class="identifier">char_</span> <span class="special">-</span> <span class="identifier">eol</span><span class="special">)</span> 67</pre> 68<p> 69 Using the <code class="computeroutput"><span class="identifier">distinct</span><span class="special">[]</span></code> 70 component instead of the explicit sequence has the advantage of being able 71 to encapsulate the tail (i.e the <code class="computeroutput"><span class="identifier">char_</span><span class="special">(</span><span class="string">"a-zA-Z_0-9"</span><span class="special">)</span></code>) as a separate parser construct. The following 72 code snippet illustrates the idea (for the full code of this example please 73 see <a href="../../../../../test/qi/distinct.cpp" target="_top">distinct.cpp</a>): 74 </p> 75<p> 76</p> 77<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">spirit</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">;</span> 78<span class="keyword">namespace</span> <span class="identifier">ascii</span> <span class="special">=</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> 79<span class="keyword">namespace</span> <span class="identifier">repo</span> <span class="special">=</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> 80 81<span class="comment">// Define metafunctions allowing to compute the type of the distinct()</span> 82<span class="comment">// and ascii::char_() constructs</span> 83<span class="keyword">namespace</span> <span class="identifier">traits</span> 84<span class="special">{</span> 85 <span class="comment">// Metafunction allowing to get the type of any repository::distinct(...) </span> 86 <span class="comment">// construct</span> 87 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Tail</span><span class="special">></span> 88 <span class="keyword">struct</span> <span class="identifier">distinct_spec</span> 89 <span class="special">:</span> <span class="identifier">spirit</span><span class="special">::</span><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">terminal</span><span class="special"><</span><span class="identifier">repo</span><span class="special">::</span><span class="identifier">tag</span><span class="special">::</span><span class="identifier">distinct</span><span class="special">(</span><span class="identifier">Tail</span><span class="special">)></span> 90 <span class="special">{};</span> 91 92 <span class="comment">// Metafunction allowing to get the type of any ascii::char_(...) construct</span> 93 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">String</span><span class="special">></span> 94 <span class="keyword">struct</span> <span class="identifier">char_spec</span> 95 <span class="special">:</span> <span class="identifier">spirit</span><span class="special">::</span><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">terminal</span><span class="special"><</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">tag</span><span class="special">::</span><span class="identifier">ascii</span><span class="special">::</span><span class="identifier">char_</span><span class="special">(</span><span class="identifier">String</span><span class="special">)></span> 96 <span class="special">{};</span> 97<span class="special">}</span> 98 99<span class="comment">// Define a helper function allowing to create a distinct() construct from </span> 100<span class="comment">// an arbitrary tail parser</span> 101<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Tail</span><span class="special">></span> 102<span class="keyword">inline</span> <span class="keyword">typename</span> <span class="identifier">traits</span><span class="special">::</span><span class="identifier">distinct_spec</span><span class="special"><</span><span class="identifier">Tail</span><span class="special">>::</span><span class="identifier">type</span> 103<span class="identifier">distinct_spec</span><span class="special">(</span><span class="identifier">Tail</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">tail</span><span class="special">)</span> 104<span class="special">{</span> 105 <span class="keyword">return</span> <span class="identifier">repo</span><span class="special">::</span><span class="identifier">distinct</span><span class="special">(</span><span class="identifier">tail</span><span class="special">);</span> 106<span class="special">}</span> 107 108<span class="comment">// Define a helper function allowing to create a ascii::char_() construct </span> 109<span class="comment">// from an arbitrary string representation</span> 110<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">String</span><span class="special">></span> 111<span class="keyword">inline</span> <span class="keyword">typename</span> <span class="identifier">traits</span><span class="special">::</span><span class="identifier">char_spec</span><span class="special"><</span><span class="identifier">String</span><span class="special">>::</span><span class="identifier">type</span> 112<span class="identifier">char_spec</span><span class="special">(</span><span class="identifier">String</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">str</span><span class="special">)</span> 113<span class="special">{</span> 114 <span class="keyword">return</span> <span class="identifier">ascii</span><span class="special">::</span><span class="identifier">char_</span><span class="special">(</span><span class="identifier">str</span><span class="special">);</span> 115<span class="special">}</span> 116 117<span class="comment">// the following constructs the type of a distinct_spec holding a</span> 118<span class="comment">// charset("0-9a-zA-Z_") as its tail parser</span> 119<span class="keyword">typedef</span> <span class="identifier">traits</span><span class="special">::</span><span class="identifier">char_spec</span><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">type</span> <span class="identifier">charset_tag_type</span><span class="special">;</span> 120<span class="keyword">typedef</span> <span class="identifier">traits</span><span class="special">::</span><span class="identifier">distinct_spec</span><span class="special"><</span><span class="identifier">charset_tag_type</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">keyword_tag_type</span><span class="special">;</span> 121 122<span class="comment">// Define a new Qi 'keyword' directive usable as a shortcut for a</span> 123<span class="comment">// repository::distinct(char_(std::string("0-9a-zA-Z_")))</span> 124<span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="keyword">const</span> <span class="identifier">keyword_spec</span><span class="special">(</span><span class="string">"0-9a-zA-Z_"</span><span class="special">);</span> 125<span class="identifier">keyword_tag_type</span> <span class="keyword">const</span> <span class="identifier">keyword</span> <span class="special">=</span> <span class="identifier">distinct_spec</span><span class="special">(</span><span class="identifier">char_spec</span><span class="special">(</span><span class="identifier">keyword_spec</span><span class="special">));</span> 126</pre> 127<p> 128 </p> 129<p> 130 These definitions define a new Qi parser recognizing keywords! This allows 131 to rewrite our declaration parser expression as: 132 </p> 133<pre class="programlisting"><span class="identifier">keyword</span><span class="special">[</span><span class="string">"description"</span><span class="special">]</span> <span class="special">>></span> <span class="special">-</span><span class="identifier">lit</span><span class="special">(</span><span class="string">":"</span><span class="special">)</span> <span class="special">>></span> <span class="special">*(</span><span class="identifier">char_</span> <span class="special">-</span> <span class="identifier">eol</span><span class="special">)</span> 134</pre> 135<p> 136 which is much more readable and concise if compared to the original parser 137 expression. In addition the new <code class="computeroutput"><span class="identifier">keyword</span><span class="special">[]</span></code> directive has the advantage to be usable 138 for wrapping any parser expression, not only strings as in the example 139 above. 140 </p> 141<h6> 142<a name="spirit_repository.qi_components.directives.distinct.h1"></a> 143 <span class="phrase"><a name="spirit_repository.qi_components.directives.distinct.header"></a></span><a class="link" href="distinct.html#spirit_repository.qi_components.directives.distinct.header">Header</a> 144 </h6> 145<pre class="programlisting"><span class="comment">// forwards to <boost/spirit/repository/home/qi/directive/distinct.hpp></span> 146<span class="preprocessor">#include</span> <span class="special"><</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_distinct</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 147</pre> 148<h6> 149<a name="spirit_repository.qi_components.directives.distinct.h2"></a> 150 <span class="phrase"><a name="spirit_repository.qi_components.directives.distinct.synopsis"></a></span><a class="link" href="distinct.html#spirit_repository.qi_components.directives.distinct.synopsis">Synopsis</a> 151 </h6> 152<pre class="programlisting"><span class="identifier">distinct</span><span class="special">(</span><span class="identifier">tail</span><span class="special">)[</span><span class="identifier">subject</span><span class="special">]</span> 153</pre> 154<h6> 155<a name="spirit_repository.qi_components.directives.distinct.h3"></a> 156 <span class="phrase"><a name="spirit_repository.qi_components.directives.distinct.parameters"></a></span><a class="link" href="distinct.html#spirit_repository.qi_components.directives.distinct.parameters">Parameters</a> 157 </h6> 158<div class="informaltable"><table class="table"> 159<colgroup> 160<col> 161<col> 162</colgroup> 163<thead><tr> 164<th> 165 <p> 166 Parameter 167 </p> 168 </th> 169<th> 170 <p> 171 Description 172 </p> 173 </th> 174</tr></thead> 175<tbody> 176<tr> 177<td> 178 <p> 179 <code class="computeroutput"><span class="identifier">tail</span></code> 180 </p> 181 </td> 182<td> 183 <p> 184 The parser construct specifying what whould not follow the subject 185 in order to match the overall expression. 186 </p> 187 </td> 188</tr> 189<tr> 190<td> 191 <p> 192 <code class="computeroutput"><span class="identifier">subject</span></code> 193 </p> 194 </td> 195<td> 196 <p> 197 The parser construct to use to match the current input. The distinct 198 directive makes sure that no unexpected partial matches occur. 199 </p> 200 </td> 201</tr> 202</tbody> 203</table></div> 204<p> 205 All two parameters can be arbitrary complex parsers themselves. 206 </p> 207<h6> 208<a name="spirit_repository.qi_components.directives.distinct.h4"></a> 209 <span class="phrase"><a name="spirit_repository.qi_components.directives.distinct.attribute"></a></span><a class="link" href="distinct.html#spirit_repository.qi_components.directives.distinct.attribute">Attribute</a> 210 </h6> 211<p> 212 The <code class="computeroutput"><span class="identifier">distinct</span></code> component 213 exposes the attribute type of its subject as its own attribute type. If 214 the <code class="computeroutput"><span class="identifier">subject</span></code> does not expose 215 any attribute (the type is <code class="computeroutput"><span class="identifier">unused_type</span></code>), 216 then the <code class="computeroutput"><span class="identifier">distinct</span></code> does 217 not expose any attribute either. 218 </p> 219<pre class="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">--></span> <span class="identifier">distinct</span><span class="special">(</span><span class="identifier">b</span><span class="special">)[</span><span class="identifier">a</span><span class="special">]:</span> <span class="identifier">A</span> 220</pre> 221<h6> 222<a name="spirit_repository.qi_components.directives.distinct.h5"></a> 223 <span class="phrase"><a name="spirit_repository.qi_components.directives.distinct.example"></a></span><a class="link" href="distinct.html#spirit_repository.qi_components.directives.distinct.example">Example</a> 224 </h6> 225<p> 226 The following example shows simple use cases of the <code class="computeroutput"><span class="identifier">distinct</span></code> 227 parser. <a href="../../../../../example/qi/distinct.cpp" target="_top">distinct.cpp</a>) 228 </p> 229<h6> 230<a name="spirit_repository.qi_components.directives.distinct.h6"></a> 231 <span class="phrase"><a name="spirit_repository.qi_components.directives.distinct.prerequisites"></a></span><a class="link" href="distinct.html#spirit_repository.qi_components.directives.distinct.prerequisites">Prerequisites</a> 232 </h6> 233<p> 234 In addition to the main header file needed to include the core components 235 implemented in <span class="emphasis"><em>Spirit.Qi</em></span> we add the header file needed 236 for the new <code class="computeroutput"><span class="identifier">distinct</span></code> generator. 237 </p> 238<p> 239</p> 240<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</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">qi</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 241<span class="preprocessor">#include</span> <span class="special"><</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_distinct</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 242</pre> 243<p> 244 </p> 245<p> 246 To make all the code below more readable we introduce the following namespaces. 247 </p> 248<p> 249</p> 250<pre class="programlisting"><span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">;</span> 251<span class="keyword">using</span> <span class="keyword">namespace</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> 252<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">distinct</span><span class="special">;</span> 253</pre> 254<p> 255 </p> 256<h6> 257<a name="spirit_repository.qi_components.directives.distinct.h7"></a> 258 <span class="phrase"><a name="spirit_repository.qi_components.directives.distinct.using_the_distinct_directive_to_match_keywords"></a></span><a class="link" href="distinct.html#spirit_repository.qi_components.directives.distinct.using_the_distinct_directive_to_match_keywords">Using 259 The Distinct Directive to Match keywords</a> 260 </h6> 261<p> 262 We show several examples of how the <code class="computeroutput"><span class="identifier">distinct</span><span class="special">[]</span></code> directive can be used to force correct 263 behavior while matching keywords. The first two code snippets show the 264 correct matching of the <code class="computeroutput"><span class="identifier">description</span></code> 265 keyword (in this hypothetical example we allow keywords to be directly 266 followed by an optional <code class="computeroutput"><span class="string">"--"</span></code>): 267 </p> 268<p> 269</p> 270<pre class="programlisting"><span class="special">{</span> 271 <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">str</span><span class="special">(</span><span class="string">"description ident"</span><span class="special">);</span> 272 <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">first</span><span class="special">(</span><span class="identifier">str</span><span class="special">.</span><span class="identifier">begin</span><span class="special">());</span> 273 <span class="keyword">bool</span> <span class="identifier">r</span> <span class="special">=</span> <span class="identifier">qi</span><span class="special">::</span><span class="identifier">phrase_parse</span><span class="special">(</span><span class="identifier">first</span><span class="special">,</span> <span class="identifier">str</span><span class="special">.</span><span class="identifier">end</span><span class="special">()</span> 274 <span class="special">,</span> <span class="identifier">distinct</span><span class="special">(</span><span class="identifier">alnum</span> <span class="special">|</span> <span class="char">'_'</span><span class="special">)[</span><span class="string">"description"</span><span class="special">]</span> <span class="special">>></span> <span class="special">-</span><span class="identifier">lit</span><span class="special">(</span><span class="string">"--"</span><span class="special">)</span> <span class="special">>></span> <span class="special">+(</span><span class="identifier">alnum</span> <span class="special">|</span> <span class="char">'_'</span><span class="special">)</span> 275 <span class="special">,</span> <span class="identifier">space</span><span class="special">);</span> 276 <span class="identifier">BOOST_ASSERT</span><span class="special">(</span><span class="identifier">r</span> <span class="special">&&</span> <span class="identifier">first</span> <span class="special">==</span> <span class="identifier">str</span><span class="special">.</span><span class="identifier">end</span><span class="special">());</span> 277<span class="special">}</span> 278</pre> 279<p> 280 </p> 281<p> 282</p> 283<pre class="programlisting"><span class="special">{</span> 284 <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">str</span><span class="special">(</span><span class="string">"description--ident"</span><span class="special">);</span> 285 <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">first</span><span class="special">(</span><span class="identifier">str</span><span class="special">.</span><span class="identifier">begin</span><span class="special">());</span> 286 <span class="keyword">bool</span> <span class="identifier">r</span> <span class="special">=</span> <span class="identifier">qi</span><span class="special">::</span><span class="identifier">phrase_parse</span><span class="special">(</span><span class="identifier">first</span><span class="special">,</span> <span class="identifier">str</span><span class="special">.</span><span class="identifier">end</span><span class="special">()</span> 287 <span class="special">,</span> <span class="identifier">distinct</span><span class="special">(</span><span class="identifier">alnum</span> <span class="special">|</span> <span class="char">'_'</span><span class="special">)[</span><span class="string">"description"</span><span class="special">]</span> <span class="special">>></span> <span class="special">-</span><span class="identifier">lit</span><span class="special">(</span><span class="string">"--"</span><span class="special">)</span> <span class="special">>></span> <span class="special">+(</span><span class="identifier">alnum</span> <span class="special">|</span> <span class="char">'_'</span><span class="special">)</span> 288 <span class="special">,</span> <span class="identifier">space</span><span class="special">);</span> 289 <span class="identifier">BOOST_ASSERT</span><span class="special">(</span><span class="identifier">r</span> <span class="special">&&</span> <span class="identifier">first</span> <span class="special">==</span> <span class="identifier">str</span><span class="special">.</span><span class="identifier">end</span><span class="special">());</span> 290<span class="special">}</span> 291</pre> 292<p> 293 </p> 294<p> 295 The last example shows that the <code class="computeroutput"><span class="identifier">distinct</span><span class="special">[]</span></code> parser component correctly refuses to 296 match "description-ident": 297 </p> 298<p> 299</p> 300<pre class="programlisting"><span class="special">{</span> 301 <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">str</span><span class="special">(</span><span class="string">"description-ident"</span><span class="special">);</span> 302 <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">::</span><span class="identifier">iterator</span> <span class="identifier">first</span><span class="special">(</span><span class="identifier">str</span><span class="special">.</span><span class="identifier">begin</span><span class="special">());</span> 303 <span class="keyword">bool</span> <span class="identifier">r</span> <span class="special">=</span> <span class="identifier">qi</span><span class="special">::</span><span class="identifier">phrase_parse</span><span class="special">(</span><span class="identifier">first</span><span class="special">,</span> <span class="identifier">str</span><span class="special">.</span><span class="identifier">end</span><span class="special">()</span> 304 <span class="special">,</span> <span class="identifier">distinct</span><span class="special">(</span><span class="identifier">alnum</span> <span class="special">|</span> <span class="char">'_'</span><span class="special">)[</span><span class="string">"description"</span><span class="special">]</span> <span class="special">>></span> <span class="special">-</span><span class="identifier">lit</span><span class="special">(</span><span class="string">"--"</span><span class="special">)</span> <span class="special">>></span> <span class="special">+(</span><span class="identifier">alnum</span> <span class="special">|</span> <span class="char">'_'</span><span class="special">)</span> 305 <span class="special">,</span> <span class="identifier">space</span><span class="special">);</span> 306 <span class="identifier">BOOST_ASSERT</span><span class="special">(!</span><span class="identifier">r</span> <span class="special">&&</span> <span class="identifier">first</span> <span class="special">==</span> <span class="identifier">str</span><span class="special">.</span><span class="identifier">begin</span><span class="special">());</span> 307<span class="special">}</span> 308</pre> 309<p> 310 </p> 311</div> 312<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 313<td align="left"></td> 314<td align="right"><div class="copyright-footer">Copyright © 2001-2011 Joel de Guzman, Hartmut Kaiser<p> 315 Distributed under the Boost Software License, Version 1.0. (See accompanying 316 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>) 317 </p> 318</div></td> 319</tr></table> 320<hr> 321<div class="spirit-nav"> 322<a accesskey="p" href="confix.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../directives.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="kwd.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 323</div> 324</body> 325</html> 326
