Re: [TSVN] issuetrackers and regex

Toby Johnson wrote:

>> Always check if the lib supports lookahead/lookbehind! There are a lot
>> of libs out there which only support a small part of the whole regex
>> specs from perl. Even Scintilla has a regex class in it, but that one
>> is very limited.
>
> I don't get why lookahead/lookbehind is so important. Couldn't the user
> simply be given the ability to specify which backreference to use as the
> bugtraq id? Is there some other aspect of lookaheads other than the
> ability to avoid using a backreference?

- there is no 'standard' for regex
- the de-facto standard is the implementation of Perl
- there's however a POSIX standard for regex, but that's not used by
most libraries because it's slower than the Perl one, hasn't as many
features and some other reasons
- Perl (and many others) have lookahead/lookbehind, which users are used
to and would miss if we wouldn't implement it too.
- Lookahead/lookbehind can be used to match a string, but only return a
part of that matched string. Example:
You want to find all numbers, which are preceeded by the word 'number'.
Without lookahead/lookbehind, the regex would always return "number
XXX", but with that feature you could write a regex which would just
return "XXX" but still make sure that it's preceeded by 'number'.

Stefan

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