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From: jk0@image.soe.clarkson.edu (Jason Coughlin)
Newsgroups: comp.lang.scheme
Subject: Non-local variables
Message-ID: <1990May8.205719.2014@sun.soe.clarkson.edu>
Date: 8 May 90 20:57:19 GMT
References: <9005081621.AA13048@mtecv2.mty.itesm.mx>
Sender: jk0@sun.soe.clarkson.edu (Jason Coughlin)
Organization: Clarkson University, Potsdam, NY
Lines: 35


	Hi.  I've got a short little example which creates a non-local
variable to implement a simple little counter.  In my implementation of
Scheme, I create it like this:

(let ([a 0])
   (define counter
      (lambda ()
	   (set! a (+ a 1))
	   a
      )
   )
)

	PC-Scheme barfs on this complaining about an illegal letrec
syntax.  Both PC-Scheme and my Scheme allow the example in Dybvig's
book, _The Scheme Programming Language_:

(define counter
   (let ([a 0])
     (lambda ()
        (set! a (+ a 1))
        a
     )
   )
)
	Am I missing something important here?


-- 
Jason Coughlin ( jk0@sun.soe.clarkson.edu , jk0@clutx )
"Every jumbled pile of person has a thinking part that wonders what the
part that isn't thinking isn't thinking of." -- They Might Be Giants
"If you read the _TV Guide_, then there's no need for a TV." -- Lost Boys