Re: [eclipse-clp-users] Another compiler bug

From: Kish Shen <kisshen_at_...5...>
Date: Mon, 23 Feb 2009 17:42:59 +0000
Hi Stephan,

Thanks for the bug report. I have taken a look at the abstract machien 
code that is generated for this program, and it does look wrong --
when the q/2 is called with C bound to 1, the indexing code incorrectly
commits to the then branch before doing the B=b unification, so that 
when the unification fails (a = b in your case), the whole query fails.

Cheers,

Kish

Stephan Schiffel wrote:
> Hi all,
> 
> I think, I found another bug (tested with version 6.0#72).
> The query p in the following program fails and prints "if" but neither "then" 
> nor "else".
> 
> p :- q(a, 1).
> 
> q(A, C) :-
>   equal([A], [B]),
>   writeln("if"),
>   (B=b, C=1 ->
>     writeln("then")
>   ;
>     writeln("else")
>   ).
> 
> equal(A, A).
> 
> The program works as expected, if the condition of the if-then-else part is 
> replaced with
>   (\+ (B\=b ; C\=1) ->
> or 
>   (\+ \+ (B=b, C=1) ->
> 
> Regards,
> Stephan
> 
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Received on Mon Feb 23 2009 - 17:43:05 CET

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