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| <p><a name="escape_char_parser"></a>The Escape Character Parser is a utility |
| parser, which parses escaped character sequences used in C/C++, |
| LEX or Perl regular expressions. Combined with the confix_p utility parser, it is useful for parsing C/C++ strings containing double quotes and other escaped |
| characters:</p> |
| <pre> confix_p<span class="special">(</span><em class="literal">'"'</em><span class="special">,</span> <span class="special">*</span>c_escape_ch_p<span class="special">,</span> <em><span class="literal">'"</span></em><span class="literal"><em>'</em></span><span class="special">)</span></pre> |
| <p>There are two different types of the Escape Character Parser: |
| <tt>c_escape_ch_p</tt>, which parses C/C++ escaped character sequences and |
| <tt>lex_escape_ch_p</tt>, which parses LEX style escaped character sequences. |
| The following table shows the valid character sequences understood by these |
| utility parsers.</p> |
| <table width="90%" border="0" align="center"> |
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| <td colspan="2" class="table_title"><b>Summary of valid escaped character |
| sequences</b></td> |
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| <td width="29%" height="27" class="table_cells"><b>c_escape_ch_p</b></td> |
| <td width="71%" class="table_cells"><p><code>\b, \t, \n, \f, \r, \\, \", |
| \', \xHH, \OOO</code><br> |
| where: H is some hexadecimal digit (0..9, a..f, A..F) and O is some octal |
| digit (0..7)</p></td> |
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| <td height="27" class="table_cells"><strong>lex_escape_ch_p</strong></td> |
| <td class="table_cells"> |
| <p>all C/C++ escaped character sequences as described above and additionally |
| any other character, which follows a backslash</p> |
| </td> |
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| </table> |
| <p>If there is a semantic action attached directly to the Escape Character Parser, |
| all valid escaped characters are converted to their character equivalent |
| (i.e. a backslash followed by a 'r' is converted to '\r'), which is |
| fed to the attached actor. The number of hexadecimal |
| or octal digits parsed depends on the size of one input character. An |
| overflow will be detected and will generate a non-match. lex_escape_ch_p |
| will strip the leading backslash for all character |
| sequences which are not listed as valid C/C++ escape sequences when passing |
| the unescaped character to an attached action.</p> |
| <p>Please note though, that if there is a semantic action attached to an |
| outermost parser (for instance as in <tt>(*c_escape_ch_p)[some_actor]</tt>, |
| where the action is attached to the kleene star generated parser) no conversion |
| takes place at the moment, but nevertheless the escaped characters are parsed |
| correctly. This limitation will be removed in a future version of the library.</p> |
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| <p class="copyright">Copyright © 2001-2002 Daniel C. Nuffer<br> |
| Copyright © 2003 Hartmut Kaiser <br> |
| <br> |
| <font size="2">Use, modification and distribution is subject to the Boost Software |
| License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at |
| http://www.boost.org/LICENSE_1_0.txt) </font> </p> |
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