Re: [Emacs-diffs] master 938d252 4/4: Make regex matching reentrant; update syntax during match

["Perry E. Metzger" <perry@piermont.com>]

On Tue, 19 Jun 2018 06:49:03 -0700 Daniel Colascione
<dancol@dancol.org> wrote:
> On 06/19/2018 06:44 AM, Perry E. Metzger wrote:
> > On Tue, 19 Jun 2018 09:40:05 -0400 "Perry E. Metzger"
> > <perry@piermont.com> wrote:  
> >> On Mon, 18 Jun 2018 10:49:46 -0700 "Daniel Colascione"
> >> <dancol@dancol.org> wrote:  
> >>>> I think the right thing would be to use TRE if we could get
> >>>> Ville Laurikari to let someone else be the maintainer. Sadly
> >>>> right now it seems unmaintained and has been for years, but
> >>>> it's fast, complete, and has the ability to handle things like
> >>>> gap buffers.  
> >>>
> >>> Last time I looked, many years ago, there were several bugs (or
> >>> differences between TRE and POSIX anyway)  
> >>
> >> Bugs yes, but the POSIX conformance was pretty strict. As I
> >> said, he seemed to have abandoned the thing, but the bones are
> >> pretty good. Someone could just fork it and implement all the
> >> patches people have been contributing that have been languishing
> >> in the github issue trackers.  
> > 
> > Oh, and re2 isn't built for POSIX compliance. It has no constructs
> > that require backtracking etc.  
> 
> No DFA engine can do backtracking.

Correct, but there are regexp libraries that will switch between DFA
and non-DFA implementations depending on whether the regexp has
constructs in it that require backtracking.

Perry
-- 
Perry E. Metzger		perry@piermont.com