936 B
936 B
Natural Transformation Examples (2/4)
data Tree a = Empty | Node a [Tree a]
toList :: Tree a -> [a]
toList Empty = []
toList (Node x l) = [x] ++ concat (map toList l)toList is a natural transformation.
It is also a morphism from Tree to [] in the Category of \(\Hask\) endofunctors.
toList . toTree = id & toTree . toList = id &therefore
[] & Tree are isomorph.