Regular expressions library

[gabor]

Hello friends!

Some time ago PBrennick asked me in a PM referring to an earlier PM whether I am still feeling like creating a reg exp library for supporting regular expression based matching. Well, I am still interested, but at first sight this is not an easy task, so I'd like to have some help. I think of comments, discussions and ideas in the first place.
As an opening I'd like to share the small specification I created while looking for Unix-like regular expression on the net.


Unix like regular expression processing

1. Basics

• Regular expressions are between '/' characters.

2. Modifiers

• i - case-insensitive match
• g - global match
• x - ignore whitespaces

3. Metacharacters must be used with \ or they have special  interpretation. (/\\/ matches a '\' character)

• \ | () [ { ^ $ * + ? .

4. Special characters

• \d - a digit
• \D - a non-digit
• \w - a word character (alphanumeric)
• \W - a non-word character
• \t - tabulator
• \n - line feed
• \r - carriage return
• \s - a whitespace character (\t,\n,\r,' ')
• \S - a non-whitespace character
• \b - word boundary
• \B - non-word boundary

5. Matching

• ^ - matches beginning of a string
• $ - matches end of a string
• . - matches any character

6. Quantifying

• * - 0 or more times (Ex. /a*/ matches '','a','aa'...)
• + - 1 or more times (Ex. /a+/ matches 'a','aa'...)
• ? - 0 or 1 time (Ex. /a?/ matches '' or 'a' only)
• {n} - exactly n times (Ex. /a{5}/: 'aaaaa')

7. Misc

• [...] - characters in the list (Ex. /[abc0-9]/ matches 'a','b','c' and digits)
• [^...] - character that are not in the list (Ex. /[^a-bA-b]/ does not match letters)
• | - alternation/or (Ex. /a|b/ matches 'a' or 'b')
• () - grouping, creates an atom that can be also referenced later
  (Ex. /(ab){2}/ matches 'abab', but ab{2} matches 'abb', /(ab)cd\1/ matches 'abcdab')[/li]

I hope this specification cover as much functionality as possible.
My problem is that this is were my knowledge neary ends :toothy. Though I have an idea but I am afraid it is not that good...
How would you implement reg.exp? Do you know about a resource about this topic on the net? Of course a fast matching method is a demand here...

Greets, Gábor

[stanhebben]

Hmm, I'll take a look at it tomorrow. At the uni, we learned quite a bit about regular expressions last year, so maybe that could help.

[PBrennick]

Gábor,
That list looks pretty comprehensive. Of special interest to Me are MetaCharacters,especially ^ $ which I use almost everday while manipulating text files. They represent The beginning of a line and the end of a line.

Paul