Path: utzoo!telly!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!gatech!tut.cis.ohio-state.edu!gem.mps.ohio-state.edu!ginosko!cs.utexas.edu!uunet!talos!kjones
From: kjones@talos.uucp (Kyle Jones)
Newsgroups: gnu.emacs.bug
Subject: Re: match data cannot always be restored
Message-ID: <1989Oct24.132350.16056@talos.uucp>
Date: 24 Oct 89 13:23:50 GMT
References: <8910201435.AA02459@ttds.tds.kth.se>
Reply-To: kjones@talos.uu.net
Distribution: gnu
Lines: 30

Juha Sarlin writes:
 > After a string-match the value of (match-beginning 0) can be zero.
 > The zero is changed into one by:
 >     (store-match-data (match-data))

This applies to clipping regions in general.  If a match-datum falls
outside the clipping region of the current buffer, it will be changed to
point-min or point-max, whichever is closer.  This is because match-data
returns match pairs as a list of markers, instead of a list of integers.
Markers, at the time of their creation, are constrained to be within the
clipping region of the buffer in which they reside.

Since match-beginning and match-end return integers, you can almost get
around this problem by building your own match-data list, i.e.

(defun integer-match-data ()
  (let ((index '(9 8 7 6 5 4 3 2 1 0))
        (list))
    (while index
      (setq list (cons (match-beginning (car index))
		       (cons (match-end (car index)) list))
	    index (cdr index)))
    list ))

Unfortunately store-match-data only accepts a list of MARKERS, so you
can't feed this list back into the regexp system.

Changing the match-data function to return integers would probably break
existing code, therefore I suggest that store-match-data be allowed to
accept integers as well as markers.