Re: Regular expressions, PCRE [was: Relation(s) between/among Kate, Kwrite, and Katepart]

[Greg Wooledge <greg@wooledge.org>]

On Mon, Apr 21, 2025 at 08:04:44 +0200, tomas@tuxteam.de wrote:
> If you like to disappear in rabbit holes, this [3] one is nice. If
> not, still the pic at the beginning still shows impressively an
> exponential runaway for Perl's re engine compared to Tcl's which
> uses a Thompson algorithm. Note that this was back in 2007 and
> quite possibly Perl's engine has been refined (it definitely has
> been extended) since then.
> 
> Cheers
> 
> [3] https://swtch.com/~rsc/regexp/regexp1.html

It still has the issue.

hobbit:~$ time perl -e '$s = "a" x 25; $r = "a?" x 25 . "a" x 25; if ($s =~ $r) { print "yes\n"; }'
yes
real 1.354  user 1.349  sys 0.004

That's with perl 5.36.0 from Bookworm.