test :- a, fail.
test :-
	( a -> writeln('a is true') ; writeln('a is false') ),
	( b -> writeln('b is true') ; writeln('b is false') ),
	( c -> writeln('c is true') ; writeln('c is false') ),
	( d -> writeln('d is true') ; writeln('d is false') ),
	( e -> writeln('e is true') ; writeln('e is false') ).

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

:- table a/0, b/0, c/0, d/0, e/0.

a :- b, c, tnot(d).

b :- e.
b.

c :- d.
c.

d :- tnot(e).

e :- b, fail.

