%------------------------------------------------------------------------
% Program that I thought it gave wrong results.
%
% Model T = {}, F = {p,q,r,s}.
%------------------------------------------------------------------------

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

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

s :- tnot(r), q.

q :- tnot(s), p.

r :- fail.

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

test :- s, fail.
test :- ( p ->	( tnot(p) -> writeln('p is undefined')
		; writeln('p is true') )
	; writeln('p is false (OK)') ),
        ( q ->  ( tnot(q) -> writeln('q is undefined')
		; writeln('q is true') )
	; writeln('q is false (OK)') ),
	( r ->  ( tnot(r) -> writeln('t is undefined')
		; writeln('r is true') )
	; writeln('r is false (OK)') ),
	( s ->  ( tnot(s) -> writeln('s is undefined')
		; writeln('s is true') )
	; writeln('s is false (OK)') ).