From: Anthony Durity <anthony.durity@...>
Date: 2006-02-07T01:28:15+09:00
Subject: Re: Merging regular expressions

Thanks Robert, thanks Dave,

I see what ye both mean. I was more thinking along the lines of a
situation like this. To avoid iterating over the array, I would like
to compress the regexps into a large regexp while still preserving the
identity of each regexp within the meta-regexp, something akin to what
happens when the scanner of a lexer is created.
So, imagine this trivial situation...

r[0] = /a/
r[1] = /b/
m = Regexp.union(r0.source, r1.source)
# _but_ when I go to check s with
m =~ s
# if it matches, i want it to tell me which of the original r[i] would
have matched!

See what I mean? Will I hack the Ruby source? Can this be done in
Ruby? Will I have to do it in C?

Thanks a million in advance again...
    Anthony

On 2/6/06, Robert Klemme <bob.news@gmx.net> wrote:
> Dave Burt wrote:
> > Anthony Durity asked:
> >> Imagine I have a bunch of n RegExps r[] - they could be any valid
> >> ruby Regexps.
> >> Say I want to match each of them in turn to a certain something s to
> >> make sure that no two Regexps in the list both match s.
> >> Now say that I want a meta regular expression m that is all the
> >> Regexps merged together so that the following pseudo code wroks,
> >>
> >> m = MetaRegExp.new
> >> for each r { [i] m.add(r[i]) } # add makes sure that no two RegExps
> >> would match the same input
> >>
> >> m =~ s # returns an int representing which of the n original RegExps
> >> would have matched
> >
> > Why not just use the array of regexps like this?
> >
> > matches = r.map{|i| r =~ s }
> > matches.index(matches.select{|i| i }[0])  # returns the int you're
> > after
>
> I guess you rather meant
>
> matches = r.map {|i| i =~ s}
> error = matches.compact.size != 1
>
> Kind regards
>
>    robert