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    1% Dual rules for q/2 and q/1 with one body variable used to clash.
    2
    3p(X) :-
    4	q(X,_).
    5
    6q(ha) :-
    7	q(a,X),
    8	X > 1.
    9
   10q(a,2).
   11
   12?- not