Oberon's FOR

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3 total messages Started by Eric W. Nikitin Fri, 12 Apr 1996 06:09

#1324

Author: Eric W. Nikitin
Date: Fri, 12 Apr 1996 06:09

11 lines
825 bytes

Questions about the FOR statement in Oberon(-2):

Is the value of the counter variable undefined upon exiting the loop -
as it is in Pascal and Modula-2?

Also, I've found that in both Oberon/F and Oberon V4 for Windows, I could 
change the counter variable within the FOR loop. I thought this was illegal
in Modula-2 - and that Oberon(-2)'s FOR loop was the same as Modula-2's.

Is it legal (as per the language definition) to change the counter within
the loop?

Re: Oberon's FOR

#1331

Author: Stephan Gehring
Date: Mon, 15 Apr 1996 06:22

31 lines
1607 bytes

In article <4kks25$hru@wariat.wariat.org>,
Eric W. Nikitin <enikitin@junior.wariat.org> wrote:
>Questions about the FOR statement in Oberon(-2):
>
>Is the value of the counter variable undefined upon exiting the loop -
>as it is in Pascal and Modula-2?

No

>Also, I've found that in both Oberon/F and Oberon V4 for Windows, I could 
>change the counter variable within the FOR loop. I thought this was illegal
>in Modula-2 - and that Oberon(-2)'s FOR loop was the same as Modula-2's.
>
>Is it legal (as per the language definition) to change the counter within
>the loop?

Yes. The Oberon-2 report defines the semantics of the FOR statment as a WHILE
statement (cf. Oberon-2 report). Since the semantics is that of a WHILE
statement

a) the counter variable may be changed within the loop body
b) the value of the counter variable is defined after exiting the loop

-- Stephan Gehring


------------------------------------------------------------------------------
Stephan Gehring                            Email:  gehring@inf.ethz.ch
Institute for Computer Systems             Phone:  +41 1 632 73 15
ETH-Zentrum                                FAX:    +41 1 632 13 07
CH-8092 Zurich, Switzerland

Re: Oberon's FOR

#1332

Author: Robert Lichtenberger
Date: Mon, 15 Apr 1996 06:41

18 lines
1120 bytes

Eric W. Nikitin (enikitin@junior.wariat.org) wrote:
: Questions about the FOR statement in Oberon(-2):
: 
: Is the value of the counter variable undefined upon exiting the loop -
: as it is in Pascal and Modula-2?
: 
: Also, I've found that in both Oberon/F and Oberon V4 for Windows, I could 
: change the counter variable within the FOR loop. I thought this was illegal
: in Modula-2 - and that Oberon(-2)'s FOR loop was the same as Modula-2's.
: 
: Is it legal (as per the language definition) to change the counter within
: the loop?
Yes it is legal, but it's _very bad_ style ;-)

-- 
Robert Lichtenberger
tanis@sport2.uibk.ac.at			k3086e1@cxmeta.edvz.uni-linz.ac.at
http://sport2.uibk.ac.at/~tanis

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