% -*-Prolog-*-

:- expects_dialect(pfc).
% this example works in a serial Pfc, but has problems in a parallel one.

p, ~a ==> b.
q, ~b ==> a.
==> p.
==> q.


% this causes problems in any Pfc, unless s is already true.
r, ~s ==> t.
t ==> s.
==> r.