%------------------------------------------------------------------------
% Program that used to give wrong results.
%
% Model T = {p}, F = {q}, U = {r}.
%------------------------------------------------------------------------

:- table p/0, q/0, r/0.

p :- tnot(q).

q :- tnot(p),tnot(r),q.

r :- tnot(p).
r :- tnot(q),tnot(r),p.

%------------------------------------------------------------------------

test :- r, fail.
test :- ( p ->	( tnot(p) -> writeln('p is undefined')
		; writeln('p is true (OK)') )
	; writeln('p is false') ),
        ( q ->  ( tnot(q) -> writeln('q is undefined')
		; writeln('q is true') )
	; writeln('q is false (OK)') ),
	( r ->  ( tnot(r) -> writeln('r is undefined (OK)')
		; writeln('r is true') )
	; writeln('r is false') ).