Errors in ISO Prolog Draft?

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3 total messages Started by Trinity College Dublin Ireland M... Mon, 31 Aug 1992 09:29

#750

Author: Trinity College Dublin Ireland M...
Date: Mon, 31 Aug 1992 09:29

16 lines
1072 bytes

I am trying to implement disjunction, if-then, if-then-else and
negation-by-failure according to ISO Prolog Draft of March 27, 1992, and I
think there may be some mistakes in the examples. Can anyone comment?

The mistakes (?) are:

Section 7.8.7.2. This is examples of if-then. The second-last example
appears to have a syntax error. I won't lose sleep worrying about that one.

Section 7.8.8.2. This is examples of if-then-else. I just don't see how the
stated behaviour of the last example can conform to the intended operation
of if-then-else. This one I worry about.

Can anyone help?

Mike

Re: Errors in ISO Prolog Draft?

#751

Author: Mats Carlsson
Date: Tue, 01 Sep 1992 07:42

22 lines
1531 bytes

In article <Trinity-College-Dublin--Ireland-310892103019@brady.cs.tcd.ie> Trinity College Dublin, Ireland (Michael Brady) writes:

   I am trying to implement disjunction, if-then, if-then-else and
   negation-by-failure according to ISO Prolog Draft of March 27, 1992, and I
   think there may be some mistakes in the examples. Can anyone comment?

   The mistakes (?) are:

   Section 7.8.7.2. This is examples of if-then. The second-last example
   appears to have a syntax error. I won't lose sleep worrying about that one.

Yes, the parentheses don't match.

   Section 7.8.8.2. This is examples of if-then-else. I just don't see how the
   stated behaviour of the last example can conform to the intended operation
   of if-then-else. This one I worry about.

Don't worry.  The example should fail on backtracking.
--
Mats Carlsson
SICS, PO Box 1263, S-164 28  KISTA, Sweden    Internet: matsc@sics.se
Tel: +46 8 7521543     Ttx: 812 6154 7010 SICS     Fax: +46 8 7517230

Re: Errors in ISO Prolog Draft?

#755

Author: David Bowen
Date: Tue, 01 Sep 1992 18:28

25 lines
1718 bytes

In article <Trinity-College-Dublin--Ireland-310892103019@brady.cs.tcd.ie>, Trinity College Dublin, Ireland (Michael Brady) writes:
> I am trying to implement disjunction, if-then, if-then-else and
> negation-by-failure according to ISO Prolog Draft of March 27, 1992, and I
> think there may be some mistakes in the examples. Can anyone comment?
> 
> The mistakes (?) are:
> 
> Section 7.8.7.2. This is examples of if-then. The second-last example
> appears to have a syntax error. I won't lose sleep worrying about that one.

Yes, this looks like a syntax error to me too.  It will be fixed.

> Section 7.8.8.2. This is examples of if-then-else. I just don't see how the
> stated behaviour of the last example can conform to the intended operation
> of if-then-else. This one I worry about.

You are right.  The example is wrong.  In the October 91 draft (N84) this 
same example was given (7.7.8.2) with the correct result -- it only succeeds 
once.

-- 
David Bowen				Vice President Product Engineering
Quintus Corporation                     InterNet:       dbowen@quintus.com
2100 Geng Road                          FAX:            415 494 7608
Palo Alto, California 94303             Phone:          415 813 3800

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