* Armin Rigo <armin.rigoatgmail.com>, 2017-01-28, 12:44:
The theoretical kind of regexp is about giving a "yes/no" answer, whereas the
concrete "re" or "regexp" modules gives a match object, which lets you ask for
the subgroups' location, for example. Strange at it may seem, I am not aware
of a way to do that using the linear-time approach of the theory---if it
answers "yes", then you have no way of knowing *where* the subgroups matched.
Another issue is that the theoretical engine has no notion of
greedy/non-greedy matching.
RE2 has linear execution time, and it supports both capture groups and
greedy/non-greedy matching.
The implementation is explained in this article:
https://swtch.com/~rsc/regexp/regexp3.html
--
Jakub Wilk
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