Re: Make regexp handling more regular

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

>>> So my idle shower thought for the day is: Is there any reasonable path
>>> forward that the Emacs Lisp language could take here?
>> 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.

E.g. we could have

    (with-re-match "regexp"
      ...
      (match-beginning 0)
      ...)

where `with-re-match` could look like

    `(if re-match-data-in-use
         (save-match-data
           ,@body)
       (let ((re-match-data-in-use t))
         ,@body))

so we'd save the match-data lazily.  [ Tho, it would still save the
match data more often than we currently do, of course.  ]
  

        Stefan