prop_univIsUnionZero :: SetOf e s => s -> Bool
prop_univIsUnionZero s = (s `union` univ) `sameAs` univ
prop_univIsUnionZero :: SetOf e s => s -> Bool
prop_univIsUnionZero s = (s `union` univ) `sameAs` univ
prop_univIsUnionZero s = (s `union` univ) `sameAs` univ