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