Re: Any performance comparison/guide of/for Emacs regex?

[Stefan Monnier]

>> Not really.  What you need to know is that Emacs's regexp engine is
>> based on backtracking, so things like .*\\(.*\\).* is insanely
>> inefficient and will make you think Emacs is frozen.
> How about if \\(.*\\) used to enclose a set of `\|'
> alternatives or for referencing in font-lock expressions?

The \(..\) subgroups are cheap, so I wouldn't worry about them
w.r.t performance.  If you really care about their performance impact,
you can use the non-numbered (aka "shy") groups which are written
\(?:...\), but I doubt you'd be able to measure a difference.


        Stefan