1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Parser</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 2.5.8"> 8<link rel="up" href="../parser_concepts.html" title="Parser Concepts"> 9<link rel="prev" href="../parser_concepts.html" title="Parser Concepts"> 10<link rel="next" href="primitiveparser.html" title="PrimitiveParser"> 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="../parser_concepts.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../parser_concepts.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="primitiveparser.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h5 class="title"> 27<a name="spirit.qi.reference.parser_concepts.parser"></a><a class="link" href="parser.html" title="Parser">Parser</a> 28</h5></div></div></div> 29<h6> 30<a name="spirit.qi.reference.parser_concepts.parser.h0"></a> 31 <span class="phrase"><a name="spirit.qi.reference.parser_concepts.parser.description"></a></span><a class="link" href="parser.html#spirit.qi.reference.parser_concepts.parser.description">Description</a> 32 </h6> 33<p> 34 The <span class="emphasis"><em>Parser</em></span> is the most fundamental concept. A Parser 35 has a member function, <code class="computeroutput"><span class="identifier">parse</span></code>, 36 that accepts a first-last <a href="http://en.cppreference.com/w/cpp/named_req/ForwardIterator" target="_top"><code class="computeroutput"><span class="identifier">ForwardIterator</span></code></a> pair and returns 37 bool as its result. The iterators delimit the data being parsed. The 38 Parser's <code class="computeroutput"><span class="identifier">parse</span></code> member 39 function returns <code class="computeroutput"><span class="keyword">true</span></code> if 40 the parse succeeds, in which case the first iterator is advanced accordingly. 41 Each Parser can represent a specific pattern or algorithm, or it can 42 be a more complex parser formed as a composition of other Parsers. 43 </p> 44<div class="variablelist"> 45<p class="title"><b>Notation</b></p> 46<dl class="variablelist"> 47<dt><span class="term"><code class="computeroutput"><span class="identifier">p</span></code></span></dt> 48<dd><p> 49 A <code class="computeroutput"><span class="identifier">Parser</span></code>. 50 </p></dd> 51<dt><span class="term"><code class="computeroutput"><span class="identifier">P</span></code></span></dt> 52<dd><p> 53 A <code class="computeroutput"><span class="identifier">Parser</span></code> type. 54 </p></dd> 55<dt><span class="term"><code class="computeroutput"><span class="identifier">Iter</span></code></span></dt> 56<dd><p> 57 a <a href="http://en.cppreference.com/w/cpp/named_req/ForwardIterator" target="_top"><code class="computeroutput"><span class="identifier">ForwardIterator</span></code></a> type. 58 </p></dd> 59<dt><span class="term"><code class="computeroutput"><span class="identifier">f</span></code>, <code class="computeroutput"><span class="identifier">l</span></code></span></dt> 60<dd><p> 61 <a href="http://en.cppreference.com/w/cpp/named_req/ForwardIterator" target="_top"><code class="computeroutput"><span class="identifier">ForwardIterator</span></code></a>. first/last 62 iterator pair. 63 </p></dd> 64<dt><span class="term"><code class="computeroutput"><span class="identifier">Context</span></code></span></dt> 65<dd><p> 66 The parser's Context type. 67 </p></dd> 68<dt><span class="term"><code class="computeroutput"><span class="identifier">context</span></code></span></dt> 69<dd><p> 70 The parser's Context, or <code class="computeroutput"><span class="identifier">unused</span></code>. 71 </p></dd> 72<dt><span class="term"><code class="computeroutput"><span class="identifier">skip</span></code></span></dt> 73<dd><p> 74 A skip Parser, or <code class="computeroutput"><span class="identifier">unused</span></code>. 75 </p></dd> 76<dt><span class="term"><code class="computeroutput"><span class="identifier">attrib</span></code></span></dt> 77<dd><p> 78 A Compatible Attribute, or <code class="computeroutput"><span class="identifier">unused</span></code>. 79 </p></dd> 80</dl> 81</div> 82<h6> 83<a name="spirit.qi.reference.parser_concepts.parser.h1"></a> 84 <span class="phrase"><a name="spirit.qi.reference.parser_concepts.parser.valid_expressions"></a></span><a class="link" href="parser.html#spirit.qi.reference.parser_concepts.parser.valid_expressions">Valid 85 Expressions</a> 86 </h6> 87<p> 88 In the expressions below, the behavior of the parser, <code class="computeroutput"><span class="identifier">p</span></code>, 89 and how <code class="computeroutput"><span class="identifier">skip</span></code> and <code class="computeroutput"><span class="identifier">attrib</span></code> are handled by <code class="computeroutput"><span class="identifier">p</span></code>, are left unspecified in the base 90 <code class="computeroutput"><span class="identifier">Parser</span></code> concept. These 91 are specified in subsequent, more refined concepts and by the actual 92 models thereof. 93 </p> 94<p> 95 For any Parser the following expressions must be valid: 96 </p> 97<div class="informaltable"><table class="table"> 98<colgroup> 99<col> 100<col> 101<col> 102</colgroup> 103<thead><tr> 104<th> 105 <p> 106 Expression 107 </p> 108 </th> 109<th> 110 <p> 111 Semantics 112 </p> 113 </th> 114<th> 115 <p> 116 Return type 117 </p> 118 </th> 119</tr></thead> 120<tbody> 121<tr> 122<td> 123 <p> 124</p> 125<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">p</span><span class="special">.</span><span class="identifier">parse</span><span class="special">(</span><span class="identifier">f</span><span class="special">,</span> <span class="identifier">l</span><span class="special">,</span> <span class="identifier">context</span><span class="special">,</span> <span class="identifier">skip</span><span class="special">,</span> <span class="identifier">attr</span><span class="special">)</span></pre> 126<p> 127 </p> 128 </td> 129<td> 130 <p> 131 Match the input sequence starting from <code class="computeroutput"><span class="identifier">f</span></code>. 132 Return <code class="computeroutput"><span class="keyword">true</span></code> if 133 successful, otherwise return <code class="computeroutput"><span class="keyword">false</span></code>. 134 </p> 135 </td> 136<td> 137 <p> 138 <code class="computeroutput"><span class="keyword">bool</span></code> 139 </p> 140 </td> 141</tr> 142<tr> 143<td> 144 <p> 145 <code class="computeroutput"><span class="identifier">p</span><span class="special">.</span><span class="identifier">what</span><span class="special">(</span><span class="identifier">context</span><span class="special">)</span></code> 146 </p> 147 </td> 148<td> 149 <p> 150 Get information about a Parser. 151 </p> 152 </td> 153<td> 154 <p> 155 <code class="computeroutput"><span class="identifier">info</span></code> 156 </p> 157 </td> 158</tr> 159</tbody> 160</table></div> 161<h6> 162<a name="spirit.qi.reference.parser_concepts.parser.h2"></a> 163 <span class="phrase"><a name="spirit.qi.reference.parser_concepts.parser.type_expressions"></a></span><a class="link" href="parser.html#spirit.qi.reference.parser_concepts.parser.type_expressions">Type 164 Expressions</a> 165 </h6> 166<div class="informaltable"><table class="table"> 167<colgroup> 168<col> 169<col> 170</colgroup> 171<thead><tr> 172<th> 173 <p> 174 Expression 175 </p> 176 </th> 177<th> 178 <p> 179 Description 180 </p> 181 </th> 182</tr></thead> 183<tbody> 184<tr> 185<td> 186 <p> 187 <code class="computeroutput"><span class="identifier">P</span><span class="special">::</span><span class="keyword">template</span> <span class="identifier">attribute</span><span class="special"><</span><span class="identifier">Context</span><span class="special">,</span> <span class="identifier">Iter</span><span class="special">>::</span><span class="identifier">type</span></code> 188 </p> 189 </td> 190<td> 191 <p> 192 The Parser's expected attribute. 193 </p> 194 </td> 195</tr> 196<tr> 197<td> 198 <p> 199 <code class="computeroutput"><span class="identifier">traits</span><span class="special">::</span><span class="identifier">is_parser</span><span class="special"><</span><span class="identifier">P</span><span class="special">>::</span><span class="identifier">type</span></code> 200 </p> 201 </td> 202<td> 203 <p> 204 Metafunction that evaluates to <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span></code> 205 if a certain type, <code class="computeroutput"><span class="identifier">P</span></code> 206 is a Parser, <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">false_</span></code> 207 otherwise (See <a href="../../../../../../../../libs/mpl/doc/refmanual/integral-constant.html" target="_top">MPL 208 Boolean Constant</a>). 209 </p> 210 </td> 211</tr> 212</tbody> 213</table></div> 214<h6> 215<a name="spirit.qi.reference.parser_concepts.parser.h3"></a> 216 <span class="phrase"><a name="spirit.qi.reference.parser_concepts.parser.postcondition"></a></span><a class="link" href="parser.html#spirit.qi.reference.parser_concepts.parser.postcondition">Postcondition</a> 217 </h6> 218<p> 219 Upon return from <code class="computeroutput"><span class="identifier">p</span><span class="special">.</span><span class="identifier">parse</span></code> the following post conditions 220 should hold: 221 </p> 222<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 223<li class="listitem"> 224 On a successful match, <code class="computeroutput"><span class="identifier">f</span></code> 225 is positioned one past the last matching character/token. 226 </li> 227<li class="listitem"> 228 On a failed match, if a <code class="computeroutput"><span class="identifier">skip</span></code> 229 parser is <code class="computeroutput"><span class="identifier">unused</span></code>, 230 <code class="computeroutput"><span class="identifier">f</span></code> is restored to 231 its original position prior to entry. 232 </li> 233<li class="listitem"> 234 On a failed match, if a <code class="computeroutput"><span class="identifier">skip</span></code> 235 parser is not <code class="computeroutput"><span class="identifier">unused</span></code>, 236 <code class="computeroutput"><span class="identifier">f</span></code> is positioned one 237 past the last character/token matching <code class="computeroutput"><span class="identifier">skip</span></code>. 238 </li> 239<li class="listitem"> 240 On a failed match, <code class="computeroutput"><span class="identifier">attrib</span></code> 241 state is undefined. 242 </li> 243<li class="listitem"> 244 No post-skips: trailing <code class="computeroutput"><span class="identifier">skip</span></code> 245 characters/tokens will not be skipped. 246 </li> 247</ul></div> 248<h6> 249<a name="spirit.qi.reference.parser_concepts.parser.h4"></a> 250 <span class="phrase"><a name="spirit.qi.reference.parser_concepts.parser.models"></a></span><a class="link" href="parser.html#spirit.qi.reference.parser_concepts.parser.models">Models</a> 251 </h6> 252<p> 253 All parsers in Spirit.Qi are models of the <span class="emphasis"><em>Parser</em></span> 254 concept. 255 </p> 256</div> 257<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 258<td align="left"></td> 259<td align="right"><div class="copyright-footer">Copyright © 2001-2011 Joel de Guzman, Hartmut Kaiser<p> 260 Distributed under the Boost Software License, Version 1.0. (See accompanying 261 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>) 262 </p> 263</div></td> 264</tr></table> 265<hr> 266<div class="spirit-nav"> 267<a accesskey="p" href="../parser_concepts.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../parser_concepts.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="primitiveparser.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 268</div> 269</body> 270</html> 271
