Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uwm.edu!zaphod.mps.ohio-state.edu!van-bc!ubc-cs!calgary!cpsc!gintera
From: gintera@cpsc.ucalgary.ca (Andrew Ginter)
Newsgroups: comp.lang.scheme
Subject: Re: Non-local variables
Summary: locally scoped variables which span procedures
Message-ID: <1990May10.003231.3064@calgary.uucp>
Date: 10 May 90 00:32:31 GMT
References: <9005081621.AA13048@mtecv2.mty.itesm.mx> <7478@accuvax.nwu.edu>
Sender: news@calgary.uucp (Network News Manager)
Organization: The University of Calgary
Lines: 18

In article <7478@accuvax.nwu.edu>, krulwich@ils.nwu.edu (Bruce Krulwich) writes:
> This is an issue that has been discussed before.  Basically, the treatment
> of internal DEFINE's as local definitions makes it impossible to have
> static locally-scoped variables that span across procedures.  (Having
> static variables for one procedure can be achieved as you showed later in
> your message.)

It seems to me that the variable "a" below is a locally scoped variable
which spans procedures...

(define dummy
  (let ((a 0))
    (list (lambda () (set! a (+ 1 a)) a)
          (lambda () (set! a (- 1 a)) a))))
(define count-up (car dummy))
(define count-down (cadr dummy))

Andrew Ginter, 403-282-2984, gintera@CPSC.UCALGARY.CA, Ginter@UNCAMULT.BITNET