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category-theory-presentation/categories/30_How/200_Monads/040_Natural_Transformation_Examples_4_4.md
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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.