| [/============================================================================== |
| Copyright (C) 2001-2010 Joel de Guzman |
| Copyright (C) 2001-2010 Hartmut Kaiser |
| |
| Distributed under 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) |
| ===============================================================================/] |
| |
| [section:lexer Supported Regular Expressions] |
| |
| [table Regular expressions support |
| [[Expression] [Meaning]] |
| [[`x`] [Match any character `x`]] |
| [[`.`] [Match any except newline (or optionally *any* character)]] |
| [[`"..."`] [All characters taken as literals between double quotes, except escape sequences]] |
| [[`[xyz]`] [A character class; in this case matches `x`, `y` or `z`]] |
| [[`[abj-oZ]`] [A character class with a range in it; matches `a`, `b` any |
| letter from `j` through `o` or a `Z`]] |
| [[`[^A-Z]`] [A negated character class i.e. any character but those in |
| the class. In this case, any character except an uppercase |
| letter]] |
| [[`r*`] [Zero or more r's (greedy), where r is any regular expression]] |
| [[`r*?`] [Zero or more r's (abstemious), where r is any regular expression]] |
| [[`r+`] [One or more r's (greedy)]] |
| [[`r+?`] [One or more r's (abstemious)]] |
| [[`r?`] [Zero or one r's (greedy), i.e. optional]] |
| [[`r??`] [Zero or one r's (abstemious), i.e. optional]] |
| [[`r{2,5}`] [Anywhere between two and five r's (greedy)]] |
| [[`r{2,5}?`] [Anywhere between two and five r's (abstemious)]] |
| [[`r{2,}`] [Two or more r's (greedy)]] |
| [[`r{2,}?`] [Two or more r's (abstemious)]] |
| [[`r{4}`] [Exactly four r's]] |
| [[`{NAME}`] [The macro `NAME` (see below)]] |
| [[`"[xyz]\"foo"`] [The literal string `[xyz]\"foo`]] |
| [[`\X`] [If X is `a`, `b`, `e`, `n`, `r`, `f`, `t`, `v` then the |
| ANSI-C interpretation of `\x`. Otherwise a literal `X` |
| (used to escape operators such as `*`)]] |
| [[`\0`] [A NUL character (ASCII code 0)]] |
| [[`\123`] [The character with octal value 123]] |
| [[`\x2a`] [The character with hexadecimal value 2a]] |
| [[`\cX`] [A named control character `X`.]] |
| [[`\a`] [A shortcut for Alert (bell).]] |
| [[`\b`] [A shortcut for Backspace]] |
| [[`\e`] [A shortcut for ESC (escape character `0x1b`)]] |
| [[`\n`] [A shortcut for newline]] |
| [[`\r`] [A shortcut for carriage return]] |
| [[`\f`] [A shortcut for form feed `0x0c`]] |
| [[`\t`] [A shortcut for horizontal tab `0x09`]] |
| [[`\v`] [A shortcut for vertical tab `0x0b`]] |
| [[`\d`] [A shortcut for `[0-9]`]] |
| [[`\D`] [A shortcut for `[^0-9]`]] |
| [[`\s`] [A shortcut for `[\x20\t\n\r\f\v]`]] |
| [[`\S`] [A shortcut for `[^\x20\t\n\r\f\v]`]] |
| [[`\w`] [A shortcut for `[a-zA-Z0-9_]`]] |
| [[`\W`] [A shortcut for `[^a-zA-Z0-9_]`]] |
| [[`(r)`] [Match an `r`; parenthesis are used to override precedence |
| (see below)]] |
| [[`(?r-s:pattern)`] [apply option 'r' and omit option 's' while interpreting pattern. |
| Options may be zero or more of the characters 'i' or 's'. |
| 'i' means case-insensitive. '-i' means case-sensitive. |
| 's' alters the meaning of the '.' syntax to match any single character whatsoever. |
| '-s' alters the meaning of '.' to match any character except '`\n`'.]] |
| [[`rs`] [The regular expression `r` followed by the regular |
| expression `s` (a sequence)]] |
| [[`r|s`] [Either an `r` or and `s`]] |
| [[`^r`] [An `r` but only at the beginning of a line (i.e. when just |
| starting to scan, or right after a newline has been |
| scanned)]] |
| [[`r`$] [An `r` but only at the end of a line (i.e. just before a |
| newline)]] |
| ] |
| |
| [note POSIX character classes are not currently supported, due to performance issues |
| when creating them in wide character mode.] |
| |
| [tip If you want to build tokens for syntaxes that recognize items like quotes |
| (`"'"`, `'"'`) and backslash (`\`), here is example syntax to get you started. |
| The lesson here really is to remember that both c++, as well as regular |
| expressions require escaping with `\` for some constructs, which can |
| cascade. |
| `` |
| quote1 = "'"; // match single "'" |
| quote2 = "\\\""; // match single '"' |
| literal_quote1 = "\\'"; // match backslash followed by single "'" |
| literal_quote2 = "\\\\\\\""; // match backslash followed by single '"' |
| literal_backslash = "\\\\\\\\"; // match two backslashes |
| `` |
| ] |
| |
| [heading Regular Expression Precedence] |
| |
| * `rs` has highest precedence |
| * `r*` has next highest (`+`, `?`, `{n,m}` have the same precedence as `*`) |
| * `r|s` has the lowest precedence |
| |
| [heading Macros] |
| |
| Regular expressions can be given a name and referred to in rules using the |
| syntax `{NAME}` where `NAME` is the name you have given to the macro. A macro |
| name can be at most 30 characters long and must start with a `_` or a letter. |
| Subsequent characters can be `_`, `-`, a letter or a decimal digit. |
| |
| [endsect] |
| |
