eval' (Eq p q) k u = eval p (\b-> if b then eval q k u else eval (Neg q) k u) u
eval' (Eq p q) k u = eval p (\b-> if b then eval q k u else eval (Neg q) k u) u
eval' (Eq p q) k u = eval p (\b-> if b then eval q k u else eval (Neg q) k u) u