Re: Make regexp handling more regular

[Juri Linkov <juri@linkov.net>]

>>> Currently the match data is like a dynamically bound variable accessible
>>> to the callee.  But maybe the match data should be only lexically-bound?
>>> (This is just a vague idea, I don't know how to implement this.)
>> Yes, I wondered whether one could use some lexical magic here, but I
>> didn't quite see what that would look like.
>
> Actually, currently the match-data is *not* like a dynamically-scoped
> var, but like a global var.  And we don't really need it to be lexically
> scoped, we would be already well-served with a dynamically-scoped var.

Notably in Ruby e.g. /(.)(.)(.)/.match("foo") returns a MatchData object:

  #<MatchData "foo" 1:"f" 2:"o" 3:"o">

Shouldn't a function like string-match (or rather some new function)
return a #<MatchData> object too?  Or the current list returned
by the function 'match-data' is sufficient?

Binding it to a variable will avoid the need to have global data
(unless global data is a requirement for performance).  Then:

  (let ((match-data (string-match regexp string)))
    (list (match-beginning subexp match-data)
          (match-end subexp match-data)))

with an additional arg MATCH-DATA added to match-processing functions:

  (match-beginning SUBEXP &optional MATCH-DATA)
  (match-end SUBEXP &optional MATCH-DATA)
  (match-string NUM &optional STRING MATCH-DATA)