1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>String Generators (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 Generators"> 9<link rel="prev" href="../string.html" title="String Generators"> 10<link rel="next" href="symbols.html" title="Symbols Generator (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.karma.reference.string.string"></a><a class="link" href="string.html" title="String Generators (string, lit)">String Generators 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.karma.reference.string.string.h0"></a> 32 <span class="phrase"><a name="spirit.karma.reference.string.string.description"></a></span><a class="link" href="string.html#spirit.karma.reference.string.string.description">Description</a> 33 </h6> 34<p> 35 The string generators described in this section are: 36 </p> 37<p> 38 The <code class="computeroutput"><span class="identifier">string</span></code> generator 39 emits a string of characters. The <code class="computeroutput"><span class="identifier">string</span></code> 40 generator is implicitly verbatim: the <code class="computeroutput"><span class="identifier">delimit</span></code> 41 parser is not applied in between characters of the string. The <code class="computeroutput"><span class="identifier">string</span></code> generator has an associated 42 <a class="link" href="../basics.html#spirit.karma.reference.basics.character_encoding_namespace">Character 43 Encoding Namespace</a>. This is needed when doing basic operations 44 such as forcing lower or upper case. Examples: 45 </p> 46<pre class="programlisting"><span class="identifier">string</span><span class="special">(</span><span class="string">"Hello"</span><span class="special">)</span> 47<span class="identifier">string</span><span class="special">(</span><span class="identifier">L</span><span class="string">"Hello"</span><span class="special">)</span> 48<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> 49</pre> 50<p> 51 <code class="computeroutput"><span class="identifier">lit</span></code>, like <code class="computeroutput"><span class="identifier">string</span></code>, also emits a string of characters. 52 The main difference is that <code class="computeroutput"><span class="identifier">lit</span></code> 53 does not consumes an attribute. A plain string like <code class="computeroutput"><span class="string">"hello"</span></code> 54 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: 55 </p> 56<pre class="programlisting"><span class="string">"Hello"</span> 57<span class="identifier">lit</span><span class="special">(</span><span class="string">"Hello"</span><span class="special">)</span> 58<span class="identifier">lit</span><span class="special">(</span><span class="identifier">L</span><span class="string">"Hello"</span><span class="special">)</span> 59<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> 60</pre> 61<h6> 62<a name="spirit.karma.reference.string.string.h1"></a> 63 <span class="phrase"><a name="spirit.karma.reference.string.string.header"></a></span><a class="link" href="string.html#spirit.karma.reference.string.string.header">Header</a> 64 </h6> 65<pre class="programlisting"><span class="comment">// forwards to <boost/spirit/home/karma/string/lit.hpp></span> 66<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">karma_string</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 67</pre> 68<p> 69 Also, see <a class="link" href="../../../structure/include.html" title="Include">Include Structure</a>. 70 </p> 71<h6> 72<a name="spirit.karma.reference.string.string.h2"></a> 73 <span class="phrase"><a name="spirit.karma.reference.string.string.namespace"></a></span><a class="link" href="string.html#spirit.karma.reference.string.string.namespace">Namespace</a> 74 </h6> 75<div class="informaltable"><table class="table"> 76<colgroup><col></colgroup> 77<thead><tr><th> 78 <p> 79 Name 80 </p> 81 </th></tr></thead> 82<tbody> 83<tr><td> 84 <p> 85 <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: 86 boost::spirit::karma::lit</span></code> 87 </p> 88 </td></tr> 89<tr><td> 90 <p> 91 <code class="computeroutput"><span class="identifier">ns</span><span class="special">::</span><span class="identifier">string</span></code> 92 </p> 93 </td></tr> 94</tbody> 95</table></div> 96<p> 97 In the table above, <code class="computeroutput"><span class="identifier">ns</span></code> 98 represents a <a class="link" href="../basics.html#spirit.karma.reference.basics.character_encoding_namespace">Character 99 Encoding Namespace</a> used by the corresponding string generator. 100 </p> 101<h6> 102<a name="spirit.karma.reference.string.string.h3"></a> 103 <span class="phrase"><a name="spirit.karma.reference.string.string.model_of"></a></span><a class="link" href="string.html#spirit.karma.reference.string.string.model_of">Model 104 of</a> 105 </h6> 106<div class="blockquote"><blockquote class="blockquote"><p> 107 <a class="link" href="../generator_concepts/primitivegenerator.html" title="PrimitiveGenerator"><code class="computeroutput"><span class="identifier">PrimitiveGenerator</span></code></a> 108 </p></blockquote></div> 109<div class="variablelist"> 110<p class="title"><b>Notation</b></p> 111<dl class="variablelist"> 112<dt><span class="term"><code class="computeroutput"><span class="identifier">s</span></code></span></dt> 113<dd><p> 114 Character-class specific string (See Character Class Types), or 115 a <a class="link" href="../basics.html#spirit.karma.reference.basics.lazy_argument">Lazy 116 Argument</a> that evaluates to a character-class specific string 117 value 118 </p></dd> 119<dt><span class="term"><code class="computeroutput"><span class="identifier">S</span></code></span></dt> 120<dd><p> 121 The type of a character-class specific string <code class="computeroutput"><span class="identifier">s</span></code>. 122 </p></dd> 123<dt><span class="term"><code class="computeroutput"><span class="identifier">ns</span></code></span></dt> 124<dd><p> 125 A <a class="link" href="../basics.html#spirit.karma.reference.basics.character_encoding_namespace">Character 126 Encoding Namespace</a>. 127 </p></dd> 128</dl> 129</div> 130<h6> 131<a name="spirit.karma.reference.string.string.h4"></a> 132 <span class="phrase"><a name="spirit.karma.reference.string.string.expression_semantics"></a></span><a class="link" href="string.html#spirit.karma.reference.string.string.expression_semantics">Expression 133 Semantics</a> 134 </h6> 135<p> 136 Semantics of an expression is defined only where it differs from, or 137 is not defined in <a class="link" href="../generator_concepts/primitivegenerator.html" title="PrimitiveGenerator"><code class="computeroutput"><span class="identifier">PrimitiveGenerator</span></code></a>. 138 </p> 139<div class="informaltable"><table class="table"> 140<colgroup> 141<col> 142<col> 143</colgroup> 144<thead><tr> 145<th> 146 <p> 147 Expression 148 </p> 149 </th> 150<th> 151 <p> 152 Description 153 </p> 154 </th> 155</tr></thead> 156<tbody> 157<tr> 158<td> 159 <p> 160 <code class="computeroutput"><span class="identifier">s</span></code> 161 </p> 162 </td> 163<td> 164 <p> 165 Generate the string literal <code class="computeroutput"><span class="identifier">s</span></code>. 166 This generator never fails (unless the underlying output stream 167 reports an error). 168 </p> 169 </td> 170</tr> 171<tr> 172<td> 173 <p> 174 <code class="computeroutput"><span class="identifier">lit</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span></code> 175 </p> 176 </td> 177<td> 178 <p> 179 Generate the string literal <code class="computeroutput"><span class="identifier">s</span></code>. 180 This generator never fails (unless the underlying output stream 181 reports an error). 182 </p> 183 </td> 184</tr> 185<tr> 186<td> 187 <p> 188 <code class="computeroutput"><span class="identifier">ns</span><span class="special">::</span><span class="identifier">string</span></code> 189 </p> 190 </td> 191<td> 192 <p> 193 Generate the string provided by a mandatory attribute interpreted 194 in the character set defined by <code class="computeroutput"><span class="identifier">ns</span></code>. 195 This generator never fails (unless the underlying output stream 196 reports an error). 197 </p> 198 </td> 199</tr> 200<tr> 201<td> 202 <p> 203 <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> 204 </p> 205 </td> 206<td> 207 <p> 208 Generate the string <code class="computeroutput"><span class="identifier">s</span></code> 209 as provided by the immediate literal value the generator is 210 initialized from. If this generator has an associated attribute 211 it succeeds only if the attribute is equal to the immediate 212 literal (unless the underlying output stream reports an error). 213 Otherwise this generator fails and does not generate any output. 214 </p> 215 </td> 216</tr> 217</tbody> 218</table></div> 219<div class="note"><table border="0" summary="Note"> 220<tr> 221<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../images/note.png"></td> 222<th align="left">Note</th> 223</tr> 224<tr><td align="left" valign="top"><p> 225 The generators <code class="computeroutput"><span class="identifier">lit</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span></code> and <code class="computeroutput"><span class="identifier">string</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span></code> can be initialized either using a 226 string literal value (i.e. <code class="computeroutput"><span class="string">"abc"</span></code>), 227 or using a <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">char_type</span><span class="special">,</span> 228 <span class="special">...></span></code>, where <code class="computeroutput"><span class="identifier">char_type</span></code> is the required value type 229 of the underlying character sequence. 230 </p></td></tr> 231</table></div> 232<div class="caution"><table border="0" summary="Caution"> 233<tr> 234<td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="../../../../images/caution.png"></td> 235<th align="left">Caution</th> 236</tr> 237<tr><td align="left" valign="top"><p> 238 The generator <code class="computeroutput"><span class="identifier">string</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span></code> up to version 2.4.1 of Spirit has 239 an undocumented feature. Given argument <code class="computeroutput"><span class="identifier">s</span></code> 240 generator succeeds as long as <code class="computeroutput"><span class="identifier">s</span></code> 241 is a prefix of given attribute. This problem has been fixed in Spirit 242 V2.4.2. 243 </p></td></tr> 244</table></div> 245<h6> 246<a name="spirit.karma.reference.string.string.h5"></a> 247 <span class="phrase"><a name="spirit.karma.reference.string.string.attributes"></a></span><a class="link" href="string.html#spirit.karma.reference.string.string.attributes">Attributes</a> 248 </h6> 249<div class="informaltable"><table class="table"> 250<colgroup> 251<col> 252<col> 253</colgroup> 254<thead><tr> 255<th> 256 <p> 257 Expression 258 </p> 259 </th> 260<th> 261 <p> 262 Attribute 263 </p> 264 </th> 265</tr></thead> 266<tbody> 267<tr> 268<td> 269 <p> 270 <code class="computeroutput"><span class="identifier">s</span></code> 271 </p> 272 </td> 273<td> 274 <p> 275 <code class="computeroutput"><span class="identifier">unused</span></code> 276 </p> 277 </td> 278</tr> 279<tr> 280<td> 281 <p> 282 <code class="computeroutput"><span class="identifier">lit</span><span class="special">(</span><span class="identifier">s</span><span class="special">)</span></code> 283 </p> 284 </td> 285<td> 286 <p> 287 <code class="computeroutput"><span class="identifier">unused</span></code> 288 </p> 289 </td> 290</tr> 291<tr> 292<td> 293 <p> 294 <code class="computeroutput"><span class="identifier">ns</span><span class="special">::</span><span class="identifier">string</span></code> 295 </p> 296 </td> 297<td> 298 <p> 299 <code class="computeroutput"><span class="identifier">S</span></code>, attribute 300 is mandatory (otherwise compilation will fail) 301 </p> 302 </td> 303</tr> 304<tr> 305<td> 306 <p> 307 <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> 308 </p> 309 </td> 310<td> 311 <p> 312 <code class="computeroutput"><span class="identifier">S</span></code>, attribute 313 is optional, if it is supplied, the generator compares the 314 attribute with <code class="computeroutput"><span class="identifier">s</span></code> 315 and succeeds only if both are equal, failing otherwise 316 </p> 317 </td> 318</tr> 319</tbody> 320</table></div> 321<div class="note"><table border="0" summary="Note"> 322<tr> 323<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../images/note.png"></td> 324<th align="left">Note</th> 325</tr> 326<tr><td align="left" valign="top"><p> 327 In addition to their usual attribute of type <code class="computeroutput"><span class="identifier">S</span></code> 328 all listed generators accept an instance of a <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special"><</span><span class="identifier">S</span><span class="special">></span></code> as well. If the <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special"><></span></code> is initialized (holds a value) 329 the generators behave as if their attribute was an instance of <code class="computeroutput"><span class="identifier">S</span></code> and emit the value stored in the 330 <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">optional</span><span class="special"><></span></code>. 331 Otherwise the generators will fail. 332 </p></td></tr> 333</table></div> 334<h6> 335<a name="spirit.karma.reference.string.string.h6"></a> 336 <span class="phrase"><a name="spirit.karma.reference.string.string.complexity"></a></span><a class="link" href="string.html#spirit.karma.reference.string.string.complexity">Complexity</a> 337 </h6> 338<div class="blockquote"><blockquote class="blockquote"><p> 339 O(N), where N is the number of characters emitted by the string generator 340 </p></blockquote></div> 341<h6> 342<a name="spirit.karma.reference.string.string.h7"></a> 343 <span class="phrase"><a name="spirit.karma.reference.string.string.example"></a></span><a class="link" href="string.html#spirit.karma.reference.string.string.example">Example</a> 344 </h6> 345<div class="note"><table border="0" summary="Note"> 346<tr> 347<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../images/note.png"></td> 348<th align="left">Note</th> 349</tr> 350<tr><td align="left" valign="top"><p> 351 The test harness for the example(s) below is presented in the <a class="link" href="../basics.html#spirit.karma.reference.basics.examples">Basics Examples</a> 352 section. 353 </p></td></tr> 354</table></div> 355<p> 356 Some includes: 357 </p> 358<p> 359</p> 360<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">karma</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 361<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">support_utree</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 362<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">phoenix_core</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 363<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">phoenix_operator</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 364<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">std_pair</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 365<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> 366<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">string</span><span class="special">></span> 367</pre> 368<p> 369 </p> 370<p> 371 Some using declarations: 372 </p> 373<p> 374</p> 375<pre class="programlisting"><span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">karma</span><span class="special">::</span><span class="identifier">lit</span><span class="special">;</span> 376<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> 377</pre> 378<p> 379 </p> 380<p> 381 Basic usage of <code class="computeroutput"><span class="identifier">string</span></code> 382 generators: 383 </p> 384<p> 385</p> 386<pre class="programlisting"><span class="identifier">test_generator</span><span class="special">(</span><span class="string">"abc"</span><span class="special">,</span> <span class="string">"abc"</span><span class="special">);</span> 387<span class="identifier">test_generator</span><span class="special">(</span><span class="string">"abc"</span><span class="special">,</span> <span class="identifier">lit</span><span class="special">(</span><span class="string">"abc"</span><span class="special">));</span> 388<span class="identifier">test_generator</span><span class="special">(</span><span class="string">"abc"</span><span class="special">,</span> <span class="identifier">lit</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="string">"abc"</span><span class="special">)));</span> 389 390<span class="identifier">test_generator_attr</span><span class="special">(</span><span class="string">"abc"</span><span class="special">,</span> <span class="identifier">string</span><span class="special">,</span> <span class="string">"abc"</span><span class="special">);</span> 391<span class="identifier">test_generator</span><span class="special">(</span><span class="string">"abc"</span><span class="special">,</span> <span class="identifier">string</span><span class="special">(</span><span class="string">"abc"</span><span class="special">));</span> 392<span class="identifier">test_generator</span><span class="special">(</span><span class="string">"abc"</span><span class="special">,</span> <span class="identifier">string</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="string">"abc"</span><span class="special">)));</span> 393 394<span class="identifier">test_generator_attr</span><span class="special">(</span><span class="string">"abc"</span><span class="special">,</span> <span class="identifier">string</span><span class="special">(</span><span class="string">"abc"</span><span class="special">),</span> <span class="string">"abc"</span><span class="special">);</span> 395<span class="identifier">test_generator_attr</span><span class="special">(</span><span class="string">""</span><span class="special">,</span> <span class="identifier">string</span><span class="special">(</span><span class="string">"abc"</span><span class="special">),</span> <span class="string">"cba"</span><span class="special">);</span> <span class="comment">// fails (as "abc" != "cba")</span> 396</pre> 397<p> 398 </p> 399</div> 400<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 401<td align="left"></td> 402<td align="right"><div class="copyright-footer">Copyright © 2001-2011 Joel de Guzman, Hartmut Kaiser<p> 403 Distributed under the Boost Software License, Version 1.0. (See accompanying 404 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>) 405 </p> 406</div></td> 407</tr></table> 408<hr> 409<div class="spirit-nav"> 410<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> 411</div> 412</body> 413</html> 414
