Michael Kifer - 2021-07-15



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Teri,


this looks like a bug in incremental tabling, as executing
abolish_all tables gives the right answer to p(1) in this case.








On 7/14/21 5:45 PM, Christophe Rey
wrote:







 [bugs:#250] unexpected answer with well founded semantics


Status: open

Group: wrong answer

Created: Wed Jul 14, 2021 09:45 PM UTC by Christophe Rey

Last Updated: Wed Jul 14, 2021 09:45 PM UTC

Owner: nobody


Hi all,

I have some unexpected results on a test program related to well founded semantics. The program is the following:


:- table p/1 as incremental.
p(X) :- tnot(qs(X)), tnot(p(X)).
p(X) :- tnot(rs(X)), tnot(p(X)).

:- table qs/1 as incremental.
qs(X) :- q(X).
:- table rs/1 as incremental.
rs(X) :- q(X).

:- dynamic q/1 as incremental.
q(1). 





The execution is:


| ?- p(1).

no
| ?- increval:incr_retract(q(1)).

yes
| ?- p(1).

undefined
| ?- increval:incr_assert(q(1)).

yes
| ?- p(1).

undefined





It is the last answer that is unexpected for me (since I thought it would be "no" as for the first query). Do I miss something? I am using XSB 4.0 under Windows.


Best regards


Christophe 




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Related

Bugs: #250