Path: utzoo!attcan!uunet!husc6!mailrus!csd4.milw.wisc.edu!markh
From: markh@csd4.milw.wisc.edu (Mark William Hopkins)
Newsgroups: comp.lang.pascal
Subject: Re: Control variables in FOR loops
Message-ID: <57@csd4.milw.wisc.edu>
Date: 23 Dec 88 02:01:56 GMT
References: <1439@csuna.UUCP> <45@csd4.milw.wisc.edu> <1771@buengc.BU.EDU>
Sender: news@csd4.milw.wisc.edu
Reply-To: markh@csd4.milw.wisc.edu (Mark William Hopkins)
Organization: University of Wisconsin-Milwaukee
Lines: 32

In article <1771@buengc.BU.EDU> art@buengc.bu.edu (A. R. Thompson) writes:
>In article <45@csd4.milw.wisc.edu> markh@csd4.milw.wisc.edu (Mark William Hopkins) writes:

<MY PROPOSED DEFINITION OF A FOR LOOP>
>>
>>for I := A to B do S       equals          I := A;
>>					     while I <= B do begin
>>                                              S;
>>						if I < B then I := succ(I)
>>					     end
>>

<COMMENTING ON THE RESULTS OF APPLYING THIS DEFINITION TO A SAMPLE PROGRAM>:
>
>Ah, but since you've already established that it's an illegal program you
>can no longer predict what will happen.  That's strictly up to the
>compiler writer (who is duty bound to report the error and refuse to
>generate executable code).  Secondarily, while your definition is the
>proper way to define the effect of the for statement it allows the control
>variable to be defined after completion of the while statement.  The
>control variable is required to be undefined upon completion of the for
>statement.

   The point I was making is that it is much easier on all counts to define
the for loop as a while loop and not place any restrictions on the control
variable.

   The real problem with the program example brought up previously was that
it used global variables, and I don't think Pascal should have allowed for
them at all.

   The for loop was merely a red herring.