1%------------------------------------------------------------------------ 2% Program for which everything is undefined. 3%------------------------------------------------------------------------ 4 5:- table p/0, q/0, r/0. 6 7p :- tnot(q). 8p :- tnot(r), fail. 9 10q :- p. 11 12r :- p. 13 14%------------------------------------------------------------------------ 15 16test :- p, fail. 17test :- 18 ( p -> 19 ( tnot(p) -> writeln('p is undefined (OK)') ; writeln('p is true') ) 20 ; writeln('p is false') ), 21 ( q -> 22 ( tnot(q) -> writeln('q is undefined (OK)') ; writeln('q is true') ) 23 ; writeln('q is false') ), 24 ( r -> 25 ( tnot(r) -> writeln('r is undefined (OK)') ; writeln('r is true') ) 26 ; writeln('r is false') ). 27