Bifunctors (simple)
newtype BiComp bf fu gu a b = BiComp (bf (fu a) (gu b))
try applying BiComp to Either,Const(),Identity,a, andb, in this order.
BiComp Either const () Id a b = BiComp (Either (const () a) (Id b)) which simplifies to Left () and Right b which is isomorphic to Nothing and Just b the two parts of Maybe! Since Functors are closed under composition and addition, its nice to see that Maybe is a Functor that we can build up out of basic parts (and such is the case for more complex ones too)














