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  26 <div class="titlepage"><div><div><h4 class="title">
  27 <a name="boost_regex.ref.syntax_option_type.syntax_option_type_perl"></a><a class="link" href="syntax_option_type_perl.html" title="Options for Perl Regular Expressions">Options
  28         for Perl Regular Expressions</a>
  29 </h4></div></div></div>
  30 <p>
  31           One of the following must always be set for perl regular expressions:
  32         </p>
  33 <div class="informaltable"><table class="table">
  34 <colgroup>
  35 <col>
  36 <col>
  37 <col>
  38 </colgroup>
  39 <thead><tr>
  40 <th>
  41                   <p>
  42                     Element
  43                   </p>
  44                 </th>
  45 <th>
  46                   <p>
  47                     Standardized
  48                   </p>
  49                 </th>
  50 <th>
  51                   <p>
  52                     Effect when set
  53                   </p>
  54                 </th>
  55 </tr></thead>
  56 <tbody>
  57 <tr>
  58 <td>
  59                   <p>
  60                     ECMAScript
  61                   </p>
  62                 </td>
  63 <td>
  64                   <p>
  65                     Yes
  66                   </p>
  67                 </td>
  68 <td>
  69                   <p>
  70                     Specifies that the grammar recognized by the regular expression
  71                     engine uses its normal semantics: that is the same as that given
  72                     in the ECMA-262, ECMAScript Language Specification, Chapter 15
  73                     part 10, RegExp (Regular Expression) Objects (FWD.1).
  74                   </p>
  75                   <p>
  76                     This is functionally identical to the <a class="link" href="../../syntax/perl_syntax.html" title="Perl Regular Expression Syntax">Perl
  77                     regular expression syntax</a>.
  78                   </p>
  79                   <p>
  80                     Boost.Regex also recognizes all of the perl-compatible <code class="computeroutput"><span class="special">(?...)</span></code> extensions in this mode.
  81                   </p>
  82                 </td>
  83 </tr>
  84 <tr>
  85 <td>
  86                   <p>
  87                     perl
  88                   </p>
  89                 </td>
  90 <td>
  91                   <p>
  92                     No
  93                   </p>
  94                 </td>
  95 <td>
  96                   <p>
  97                     As above.
  98                   </p>
  99                 </td>
 100 </tr>
 101 <tr>
 102 <td>
 103                   <p>
 104                     normal
 105                   </p>
 106                 </td>
 107 <td>
 108                   <p>
 109                     No
 110                   </p>
 111                 </td>
 112 <td>
 113                   <p>
 114                     As above.
 115                   </p>
 116                 </td>
 117 </tr>
 118 <tr>
 119 <td>
 120                   <p>
 121                     JavaScript
 122                   </p>
 123                 </td>
 124 <td>
 125                   <p>
 126                     No
 127                   </p>
 128                 </td>
 129 <td>
 130                   <p>
 131                     As above.
 132                   </p>
 133                 </td>
 134 </tr>
 135 <tr>
 136 <td>
 137                   <p>
 138                     JScript
 139                   </p>
 140                 </td>
 141 <td>
 142                   <p>
 143                     No
 144                   </p>
 145                 </td>
 146 <td>
 147                   <p>
 148                     As above.
 149                   </p>
 150                 </td>
 151 </tr>
 152 </tbody>
 153 </table></div>
 154 <p>
 155           The following options may also be set when using perl-style regular expressions:
 156         </p>
 157 <div class="informaltable"><table class="table">
 158 <colgroup>
 159 <col>
 160 <col>
 161 <col>
 162 </colgroup>
 163 <thead><tr>
 164 <th>
 165                   <p>
 166                     Element
 167                   </p>
 168                 </th>
 169 <th>
 170                   <p>
 171                     Standardized
 172                   </p>
 173                 </th>
 174 <th>
 175                   <p>
 176                     Effect when set
 177                   </p>
 178                 </th>
 179 </tr></thead>
 180 <tbody>
 181 <tr>
 182 <td>
 183                   <p>
 184                     icase
 185                   </p>
 186                 </td>
 187 <td>
 188                   <p>
 189                     Yes
 190                   </p>
 191                 </td>
 192 <td>
 193                   <p>
 194                     Specifies that matching of regular expressions against a character
 195                     container sequence shall be performed without regard to case.
 196                   </p>
 197                 </td>
 198 </tr>
 199 <tr>
 200 <td>
 201                   <p>
 202                     nosubs
 203                   </p>
 204                 </td>
 205 <td>
 206                   <p>
 207                     Yes
 208                   </p>
 209                 </td>
 210 <td>
 211                   <p>
 212                     Specifies that when a regular expression is matched against a
 213                     character container sequence, then no sub-expression matches
 214                     are to be stored in the supplied <a class="link" href="../match_results.html" title="match_results"><code class="computeroutput"><span class="identifier">match_results</span></code></a> structure.
 215                   </p>
 216                 </td>
 217 </tr>
 218 <tr>
 219 <td>
 220                   <p>
 221                     optimize
 222                   </p>
 223                 </td>
 224 <td>
 225                   <p>
 226                     Yes
 227                   </p>
 228                 </td>
 229 <td>
 230                   <p>
 231                     Specifies that the regular expression engine should pay more
 232                     attention to the speed with which regular expressions are matched,
 233                     and less to the speed with which regular expression objects are
 234                     constructed. Otherwise it has no detectable effect on the program
 235                     output. This currently has no effect for Boost.Regex.
 236                   </p>
 237                 </td>
 238 </tr>
 239 <tr>
 240 <td>
 241                   <p>
 242                     collate
 243                   </p>
 244                 </td>
 245 <td>
 246                   <p>
 247                     Yes
 248                   </p>
 249                 </td>
 250 <td>
 251                   <p>
 252                     Specifies that character ranges of the form <code class="computeroutput"><span class="special">[</span><span class="identifier">a</span><span class="special">-</span><span class="identifier">b</span><span class="special">]</span></code>
 253                     should be locale sensitive.
 254                   </p>
 255                 </td>
 256 </tr>
 257 <tr>
 258 <td>
 259                   <p>
 260                     newline_alt
 261                   </p>
 262                 </td>
 263 <td>
 264                   <p>
 265                     No
 266                   </p>
 267                 </td>
 268 <td>
 269                   <p>
 270                     Specifies that the \n character has the same effect as the alternation
 271                     operator |. Allows newline separated lists to be used as a list
 272                     of alternatives.
 273                   </p>
 274                 </td>
 275 </tr>
 276 <tr>
 277 <td>
 278                   <p>
 279                     no_except
 280                   </p>
 281                 </td>
 282 <td>
 283                   <p>
 284                     No
 285                   </p>
 286                 </td>
 287 <td>
 288                   <p>
 289                     Prevents <a class="link" href="../basic_regex.html" title="basic_regex"><code class="computeroutput"><span class="identifier">basic_regex</span></code></a> from throwing
 290                     an exception when an invalid expression is encountered.
 291                   </p>
 292                 </td>
 293 </tr>
 294 <tr>
 295 <td>
 296                   <p>
 297                     no_mod_m
 298                   </p>
 299                 </td>
 300 <td>
 301                   <p>
 302                     No
 303                   </p>
 304                 </td>
 305 <td>
 306                   <p>
 307                     Normally Boost.Regex behaves as if the Perl m-modifier is on:
 308                     so the assertions ^ and $ match after and before embedded newlines
 309                     respectively, setting this flags is equivalent to prefixing the
 310                     expression with (?-m).
 311                   </p>
 312                 </td>
 313 </tr>
 314 <tr>
 315 <td>
 316                   <p>
 317                     no_mod_s
 318                   </p>
 319                 </td>
 320 <td>
 321                   <p>
 322                     No
 323                   </p>
 324                 </td>
 325 <td>
 326                   <p>
 327                     Normally whether Boost.Regex will match "." against
 328                     a newline character is determined by the match flag <code class="computeroutput"><span class="identifier">match_dot_not_newline</span></code>. Specifying
 329                     this flag is equivalent to prefixing the expression with <code class="computeroutput"><span class="special">(?-</span><span class="identifier">s</span><span class="special">)</span></code> and therefore causes "."
 330                     not to match a newline character regardless of whether <code class="computeroutput"><span class="identifier">match_not_dot_newline</span></code> is set
 331                     in the match flags.
 332                   </p>
 333                 </td>
 334 </tr>
 335 <tr>
 336 <td>
 337                   <p>
 338                     mod_s
 339                   </p>
 340                 </td>
 341 <td>
 342                   <p>
 343                     No
 344                   </p>
 345                 </td>
 346 <td>
 347                   <p>
 348                     Normally whether Boost.Regex will match "." against
 349                     a newline character is determined by the match flag <code class="computeroutput"><span class="identifier">match_dot_not_newline</span></code>. Specifying
 350                     this flag is equivalent to prefixing the expression with <code class="computeroutput"><span class="special">(?</span><span class="identifier">s</span><span class="special">)</span></code> and therefore causes "."
 351                     to match a newline character regardless of whether <code class="computeroutput"><span class="identifier">match_not_dot_newline</span></code> is set
 352                     in the match flags.
 353                   </p>
 354                 </td>
 355 </tr>
 356 <tr>
 357 <td>
 358                   <p>
 359                     mod_x
 360                   </p>
 361                 </td>
 362 <td>
 363                   <p>
 364                     No
 365                   </p>
 366                 </td>
 367 <td>
 368                   <p>
 369                     Turns on the perl x-modifier: causes unescaped whitespace in
 370                     the expression to be ignored.
 371                   </p>
 372                 </td>
 373 </tr>
 374 <tr>
 375 <td>
 376                   <p>
 377                     no_empty_expressions
 378                   </p>
 379                 </td>
 380 <td>
 381                   <p>
 382                     No
 383                   </p>
 384                 </td>
 385 <td>
 386                   <p>
 387                     When set then empty expressions/alternatives are prohibited.
 388                   </p>
 389                 </td>
 390 </tr>
 391 <tr>
 392 <td>
 393                   <p>
 394                     save_subexpression_location
 395                   </p>
 396                 </td>
 397 <td>
 398                   <p>
 399                     No
 400                   </p>
 401                 </td>
 402 <td>
 403                   <p>
 404                     When set then the locations of individual sub-expressions within
 405                     the <span class="emphasis"><em>original regular expression string</em></span> can
 406                     be accessed via the <a class="link" href="../basic_regex.html#boost_regex.basic_regex.subexpression"><code class="computeroutput"><span class="identifier">subexpression</span><span class="special">()</span></code></a>
 407                     member function of <code class="computeroutput"><span class="identifier">basic_regex</span></code>.
 408                   </p>
 409                 </td>
 410 </tr>
 411 </tbody>
 412 </table></div>
 413 </div>
 414 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 415 <td align="left"></td>
 416 <td align="right"><div class="copyright-footer">Copyright &#169; 1998-2013 John Maddock<p>
 417         Distributed under the Boost Software License, Version 1.0. (See accompanying
 418         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>)
 419       </p>
 420 </div></td>
 421 </tr></table>
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