perm filename PROLOG.LOG[1,JMC] blob sn#789507 filedate 1985-04-02 generic text, type T, neo UTF8
| holds(imp(p,q)).
| holds(p).
| holds(Q) :- holds(imp(P,Q)),holds(P).
| ?-holds(q).

yes
| holds(r).
| ?-holds(s).