Composition Rule for Covariant and Contravariant Parameters

By the rule of composition, contravariant parameters composed as an intersection (i.e. with &) are equivalent to covariant parameters composed together as a union (i.e. with |)

By the rule of composition, contravariant parameters composed as an intersection (i.e. with &) are equivalent to covariant parameters composed together as a union (i.e. with |)