You might already know the map function: map :: (a -> b) -> [a] -> [b] map _ [] = [] map f (x:xs) = f x : map f xs > map (\x -> x + 1) [1, 2, 3] [2, 3, 4] It takes a function of type a -> b and applies it to each element of a list. The elements change, but the data type storing them ([]) remains the same. In this article, we’ll call such a data type with another type inside it a context. Transform