Re: Perl, etc has these "?"-prefix modifiers/codes/whatever. Precisely which does emacs have (and NOT have)?

[Stefan Monnier <monnier@iro.umontreal.ca>]

> Please, someone, make an ascii or html table or even plain text 
> list of all these neat "new" non-standard ops that perl and
> even php and ruby etc seem to have now, comparing them
> to what Emacs has or don't have.

As mentioned, Emacs regexps are fairly well described in the Emacs
manual and the Elisp manual.

Indeed Emacs regexps don't support all the fancy additions present in
things like Perl.  IIRC someone provided a patch for the look-ahead and
look-behind features, but it got lost somewhere along the way.

Emacs likes regexps, so it makes sense to support these things.  At the
same time, I've known them for a long time but have rarely found a need
for them in my Emacs experience.

Personally I'd like to add a DFA-based regex engine to Emacs, so as to
get rid of the exponential backtracking problem that shows up every once
in a while (it also has a few other advantages, such as the ability to
do the regexp matching a chunk at a time).


        Stefan