1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>String Parsers (string, lit)</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="../string.html" title="String Parsers"> 9<link rel="prev" href="../string.html" title="String Parsers"> 10<link rel="next" href="symbols.html" title="Symbols Parser (symbols)"> 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="../string.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../string.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="symbols.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.string.string"></a><a class="link" href="string.html" title="String Parsers (string, lit)">String Parsers 28 (<code class="computeroutput"><span class="identifier">string</span></code>, <code class="computeroutput"><span class="identifier">lit</span></code>)</a> 29</h5></div></div></div> 30<h6> 31<a name="spirit.qi.reference.string.string.h0"></a> 32 <span class="phrase"><a name="spirit.qi.reference.string.string.description"></a></span><a class="link" href="string.html#spirit.qi.reference.string.string.description">Description</a> 33 </h6> 34<p> 35 The <code class="computeroutput"><span class="identifier">string</span></code> parser matches 36 a string of characters. The <code class="computeroutput"><span class="identifier">string</span></code> 37 parser is an implicit lexeme: the <code class="computeroutput"><span class="identifier">skip</span></code> 38 parser is not applied in between characters of the string. The <code class="computeroutput"><span class="identifier">string</span></code> parser has an associated <a class="link" href="../basics.html#spirit.qi.reference.basics.character_encoding_namespace">Character 39 Encoding Namespace</a>. This is needed when doing basic operations 40 such as inhibiting case sensitivity. Examples: 41 </p> 42<pre class="programlisting"><span class="identifier">string</span><span class="special">(</span><span class="string">"Hello"</span><span class="special">)</span> 43<span class="identifier">string</span><span class="special">(</span><span class="identifier">L</span><span class="string">"Hello"</span><span class="special">)</span> 44<span class="identifier">string</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span> <span class="comment">// s is a std::string</span> 45</pre> 46<p> 47 <code class="computeroutput"><span class="identifier">lit</span></code>, like <code class="computeroutput"><span class="identifier">string</span></code>, also matches a string of characters. 48 The main difference is that <code class="computeroutput"><span class="identifier">lit</span></code> 49 does not synthesize an attribute. A plain string like <code class="computeroutput"><span class="string">"hello"</span></code> 50 or a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_string</span></code> is equivalent to a <code class="computeroutput"><span class="identifier">lit</span></code>. Examples: 51 </p> 52<pre class="programlisting"><span class="string">"Hello"</span> 53<span class="identifier">lit</span><span class="special">(</span><span class="string">"Hello"</span><span class="special">)</span> 54<span class="identifier">lit</span><span class="special">(</span><span class="identifier">L</span><span class="string">"Hello"</span><span class="special">)</span> 55<span class="identifier">lit</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span> <span class="comment">// s is a std::string</span> 56</pre> 57<h6> 58<a name="spirit.qi.reference.string.string.h1"></a> 59 <span class="phrase"><a name="spirit.qi.reference.string.string.header"></a></span><a class="link" href="string.html#spirit.qi.reference.string.string.header">Header</a> 60 </h6> 61<pre class="programlisting"><span class="comment">// forwards to <boost/spirit/home/qi/string/lit.hpp></span> 62<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_lit</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 63</pre> 64<h6> 65<a name="spirit.qi.reference.string.string.h2"></a> 66 <span class="phrase"><a name="spirit.qi.reference.string.string.namespace"></a></span><a class="link" href="string.html#spirit.qi.reference.string.string.namespace">Namespace</a> 67 </h6> 68<div class="informaltable"><table class="table"> 69<colgroup><col></colgroup> 70<thead><tr><th> 71 <p> 72 Name 73 </p> 74 </th></tr></thead> 75<tbody> 76<tr><td> 77 <p> 78 <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: 79 boost::spirit::qi::lit</span></code> 80 </p> 81 </td></tr> 82<tr><td> 83 <p> 84 <code class="computeroutput"><span class="identifier">ns</span><span class="special">::</span><span class="identifier">string</span></code> 85 </p> 86 </td></tr> 87</tbody> 88</table></div> 89<p> 90 In the table above, <code class="computeroutput"><span class="identifier">ns</span></code> 91 represents a <a class="link" href="../basics.html#spirit.qi.reference.basics.character_encoding_namespace">Character 92 Encoding Namespace</a>. 93 </p> 94<h6> 95<a name="spirit.qi.reference.string.string.h3"></a> 96 <span class="phrase"><a name="spirit.qi.reference.string.string.model_of"></a></span><a class="link" href="string.html#spirit.qi.reference.string.string.model_of">Model 97 of</a> 98 </h6> 99<div class="blockquote"><blockquote class="blockquote"><p> 100 <a class="link" href="../parser_concepts/primitiveparser.html" title="PrimitiveParser"><code class="computeroutput"><span class="identifier">PrimitiveParser</span></code></a> 101 </p></blockquote></div> 102<div class="variablelist"> 103<p class="title"><b>Notation</b></p> 104<dl class="variablelist"> 105<dt><span class="term"><code class="computeroutput"><span class="identifier">s</span></code></span></dt> 106<dd><p> 107 A <a class="link" href="../basics.html#spirit.qi.reference.basics.string">String</a> 108 or a <a class="link" href="../basics.html#spirit.qi.reference.basics.lazy_argument">Lazy 109 Argument</a> that evaluates to a <a class="link" href="../basics.html#spirit.qi.reference.basics.string">String</a>. 110 </p></dd> 111<dt><span class="term"><code class="computeroutput"><span class="identifier">ns</span></code></span></dt> 112<dd><p> 113 A <a class="link" href="../basics.html#spirit.qi.reference.basics.character_encoding_namespace">Character 114 Encoding Namespace</a>. 115 </p></dd> 116</dl> 117</div> 118<h6> 119<a name="spirit.qi.reference.string.string.h4"></a> 120 <span class="phrase"><a name="spirit.qi.reference.string.string.expression_semantics"></a></span><a class="link" href="string.html#spirit.qi.reference.string.string.expression_semantics">Expression 121 Semantics</a> 122 </h6> 123<p> 124 Semantics of an expression is defined only where it differs from, or 125 is not defined in <a class="link" href="../parser_concepts/primitiveparser.html" title="PrimitiveParser"><code class="computeroutput"><span class="identifier">PrimitiveParser</span></code></a>. 126 </p> 127<div class="informaltable"><table class="table"> 128<colgroup> 129<col> 130<col> 131</colgroup> 132<thead><tr> 133<th> 134 <p> 135 Expression 136 </p> 137 </th> 138<th> 139 <p> 140 Semantics 141 </p> 142 </th> 143</tr></thead> 144<tbody> 145<tr> 146<td> 147 <p> 148 <code class="computeroutput"><span class="identifier">s</span></code> 149 </p> 150 </td> 151<td> 152 <p> 153 Create string parser from a string, <code class="computeroutput"><span class="identifier">s</span></code>. 154 </p> 155 </td> 156</tr> 157<tr> 158<td> 159 <p> 160 <code class="computeroutput"><span class="identifier">lit</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span></code> 161 </p> 162 </td> 163<td> 164 <p> 165 Create a string parser from a string, <code class="computeroutput"><span class="identifier">s</span></code>. 166 </p> 167 </td> 168</tr> 169<tr> 170<td> 171 <p> 172 <code class="computeroutput"><span class="identifier">ns</span><span class="special">::</span><span class="identifier">string</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span></code> 173 </p> 174 </td> 175<td> 176 <p> 177 Create a string parser with <code class="computeroutput"><span class="identifier">ns</span></code> 178 encoding from a string, <code class="computeroutput"><span class="identifier">s</span></code>. 179 </p> 180 </td> 181</tr> 182</tbody> 183</table></div> 184<h6> 185<a name="spirit.qi.reference.string.string.h5"></a> 186 <span class="phrase"><a name="spirit.qi.reference.string.string.attributes"></a></span><a class="link" href="string.html#spirit.qi.reference.string.string.attributes">Attributes</a> 187 </h6> 188<div class="informaltable"><table class="table"> 189<colgroup> 190<col> 191<col> 192</colgroup> 193<thead><tr> 194<th> 195 <p> 196 Expression 197 </p> 198 </th> 199<th> 200 <p> 201 Attribute 202 </p> 203 </th> 204</tr></thead> 205<tbody> 206<tr> 207<td> 208 <p> 209 <code class="computeroutput"><span class="identifier">s</span></code> 210 </p> 211 </td> 212<td> 213 <p> 214 <code class="computeroutput"><span class="identifier">unused</span></code> 215 </p> 216 </td> 217</tr> 218<tr> 219<td> 220 <p> 221 <code class="computeroutput"><span class="identifier">lit</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span></code> 222 </p> 223 </td> 224<td> 225 <p> 226 <code class="computeroutput"><span class="identifier">unused</span></code> 227 </p> 228 </td> 229</tr> 230<tr> 231<td> 232 <p> 233 <code class="computeroutput"><span class="identifier">ns</span><span class="special">::</span><span class="identifier">string</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span></code> 234 </p> 235 </td> 236<td> 237 <p> 238 <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_string</span><span class="special"><</span><span class="identifier">T</span><span class="special">></span></code> 239 where <code class="computeroutput"><span class="identifier">T</span></code> is 240 the underlying character type of <code class="computeroutput"><span class="identifier">s</span></code>. 241 </p> 242 </td> 243</tr> 244</tbody> 245</table></div> 246<h6> 247<a name="spirit.qi.reference.string.string.h6"></a> 248 <span class="phrase"><a name="spirit.qi.reference.string.string.complexity"></a></span><a class="link" href="string.html#spirit.qi.reference.string.string.complexity">Complexity</a> 249 </h6> 250<div class="blockquote"><blockquote class="blockquote"><p> 251 O(N) 252 </p></blockquote></div> 253<p> 254 where <code class="computeroutput"><span class="identifier">N</span></code> is the number 255 of characters in the string to be parsed. 256 </p> 257<h6> 258<a name="spirit.qi.reference.string.string.h7"></a> 259 <span class="phrase"><a name="spirit.qi.reference.string.string.example"></a></span><a class="link" href="string.html#spirit.qi.reference.string.string.example">Example</a> 260 </h6> 261<div class="note"><table border="0" summary="Note"> 262<tr> 263<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../images/note.png"></td> 264<th align="left">Note</th> 265</tr> 266<tr><td align="left" valign="top"><p> 267 The test harness for the example(s) below is presented in the <a class="link" href="../basics.html#spirit.qi.reference.basics.examples">Basics Examples</a> 268 section. 269 </p></td></tr> 270</table></div> 271<p> 272 Some using declarations: 273 </p> 274<p> 275</p> 276<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">qi</span><span class="special">::</span><span class="identifier">lit</span><span class="special">;</span> 277<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">string</span><span class="special">;</span> 278</pre> 279<p> 280 </p> 281<p> 282 Basic literals: 283 </p> 284<p> 285</p> 286<pre class="programlisting"><span class="identifier">test_parser</span><span class="special">(</span><span class="string">"boost"</span><span class="special">,</span> <span class="string">"boost"</span><span class="special">);</span> <span class="comment">// plain literal</span> 287<span class="identifier">test_parser</span><span class="special">(</span><span class="string">"boost"</span><span class="special">,</span> <span class="identifier">lit</span><span class="special">(</span><span class="string">"boost"</span><span class="special">));</span> <span class="comment">// explicit literal</span> 288<span class="identifier">test_parser</span><span class="special">(</span><span class="string">"boost"</span><span class="special">,</span> <span class="identifier">string</span><span class="special">(</span><span class="string">"boost"</span><span class="special">));</span> <span class="comment">// ascii::string</span> 289</pre> 290<p> 291 </p> 292<p> 293 From a <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span></code> 294 </p> 295<p> 296</p> 297<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">s</span><span class="special">(</span><span class="string">"boost"</span><span class="special">);</span> 298<span class="identifier">test_parser</span><span class="special">(</span><span class="string">"boost"</span><span class="special">,</span> <span class="identifier">s</span><span class="special">);</span> <span class="comment">// direct</span> 299<span class="identifier">test_parser</span><span class="special">(</span><span class="string">"boost"</span><span class="special">,</span> <span class="identifier">lit</span><span class="special">(</span><span class="identifier">s</span><span class="special">));</span> <span class="comment">// explicit</span> 300<span class="identifier">test_parser</span><span class="special">(</span><span class="string">"boost"</span><span class="special">,</span> <span class="identifier">string</span><span class="special">(</span><span class="identifier">s</span><span class="special">));</span> <span class="comment">// ascii::string</span> 301</pre> 302<p> 303 </p> 304<p> 305 Lazy strings using <a href="../../../../../../../../libs/phoenix/doc/html/index.html" target="_top">Boost.Phoenix</a> 306 </p> 307<p> 308</p> 309<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">phx</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">phoenix</span><span class="special">;</span> 310<span class="identifier">test_parser</span><span class="special">(</span><span class="string">"boost"</span><span class="special">,</span> <span class="identifier">phx</span><span class="special">::</span><span class="identifier">val</span><span class="special">(</span><span class="string">"boost"</span><span class="special">));</span> <span class="comment">// direct</span> 311<span class="identifier">test_parser</span><span class="special">(</span><span class="string">"boost"</span><span class="special">,</span> <span class="identifier">lit</span><span class="special">(</span><span class="identifier">phx</span><span class="special">::</span><span class="identifier">val</span><span class="special">(</span><span class="string">"boost"</span><span class="special">)));</span> <span class="comment">// explicit</span> 312<span class="identifier">test_parser</span><span class="special">(</span><span class="string">"boost"</span><span class="special">,</span> <span class="identifier">string</span><span class="special">(</span><span class="identifier">phx</span><span class="special">::</span><span class="identifier">val</span><span class="special">(</span><span class="string">"boost"</span><span class="special">)));</span> <span class="comment">// ascii::string</span> 313</pre> 314<p> 315 </p> 316</div> 317<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 318<td align="left"></td> 319<td align="right"><div class="copyright-footer">Copyright © 2001-2011 Joel de Guzman, Hartmut Kaiser<p> 320 Distributed under the Boost Software License, Version 1.0. (See accompanying 321 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>) 322 </p> 323</div></td> 324</tr></table> 325<hr> 326<div class="spirit-nav"> 327<a accesskey="p" href="../string.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../string.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="symbols.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 328</div> 329</body> 330</html> 331
