prop_emptyHasSizeZero :: SetOf e s => s -> Bool
prop_emptyHasSizeZero s = (s `sameAs` empty) == (isZero (size s))
prop_emptyHasSizeZero :: SetOf e s => s -> Bool
prop_emptyHasSizeZero s = (s `sameAs` empty) == (isZero (size s))
prop_emptyHasSizeZero s = (s `sameAs` empty) == (isZero (size s))