i think the way you defined it, covariant and contravariant are identical; in your contravariant definition, swap the names of "A" and "B" and you get: if B

i think the way you defined it, covariant and contravariant are identical; in your contravariant definition, swap the names of "A" and "B" and you get: if B >: A, then F[A] <: F[B] and B >: A means the same as A <: B, so this means: if A <: B, then F[A] <: F[B] which is the same as your covariant definition. Perhaps you meant: If F[_] is "contravariant", it means that if A <: B, then F[B] <: F[A] ?