prop_intersectionWithSelfIsSelf :: SetOf e s => s -> Bool
prop_intersectionWithSelfIsSelf s = (s `intersection` s) `sameAs` s
prop_intersectionWithSelfIsSelf :: SetOf e s => s -> Bool
prop_intersectionWithSelfIsSelf s = (s `intersection` s) `sameAs` s
prop_intersectionWithSelfIsSelf s = (s `intersection` s) `sameAs` s