Natural Transformation Examples (4/4)

mToList :: Maybe a -> [a]
mToList Nothing = []
mToList Just x  = [x]

toMaybe is a natural transformation. It is also a morphism from [] to Maybe in the Category of \(\Hask\) endofunctors.

natural transformation commutative diagram

relation between [] and Maybe — There is no isomorphism.
Hint: `Bool` lists longer than 1.