%------------------------------------------------------------------------
%  Dynamically stratified program in which p is FALSE no matter what!
%  (even though it might require answer completion for its second clause).
%------------------------------------------------------------------------

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

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

q :- tnot(r).

r :- tnot(p), fail.

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

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