Capturing groups and searches

Question

I want to know how capture groups (or non-capture ones) affect search queries in Regex. Here are two examples:

test (?:(?!<start).)+

test (?!<start).+

I would appreciate it if anyone could explain how the regex mechanism interprets both cases in detail.

+3

Pablo May 23 '11 at 6:56

1 answer

Kobi · Answer 1 · 2011-05-23T08:03:09+0000

Appearance zero width . In this regard, it makes no sense to place them yourself inside the capture group, they do not capture anything more interesting than an empty line (just like \b vs. (\b)._{^{. backlink to an optional group, but this is not very interesting.}}
looharounds - (?=...) (?<=...) - . , /(?=(\b\w+\b))/ , . , /(?<=(.))\1/ , .
looharounds - (?!...) (?<!...) - . , , , . , ^(?!.*(.).*\1).*$ , . _{^{, \1, .}}

, . :

(?:(?!<start).)+ - , start, (). :
- "start1234end", - "".
- "before123startAfter" , "before123start" ( ), : "fter".
(?:(?!<start).)+ - lookbehind ( : (?:...)+ , ). , start:
- "start1234end" - "start". '1' ( , start), . "234end".