1query(p89,p,[p,q,r,s],[p,r],[]).
2%-----------------------------------------------------------
3
4:- table p / 0.
5:- table q / 0.
6:- table r / 0.
7:- table s / 0.
8
9p :- tnot(q), r.
10q :- tnot(p), s.
11r.
12s :- fail.
13