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:
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** [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