Data.List

data List a

A finite sequence of values of the same type.

Nil :: List a

Cons :: a -> List a -> List a

map :: forall a b. (a -> b) -> List a -> List b

Transform each element, retaining the order of the input.

map (\x -> x * 2) [1, 2, 3]
-- [2, 4, 6]

foldr :: forall a b. (a -> b -> b) -> b -> List a -> b

Fold a list from the right using a combining function and an initial value.

length :: forall a. List a -> Nat

Count the elements in a finite list.

length [1, 2, 3]
-- 3

head :: forall a. List a -> Option a

Return the first element when present. An empty list produces None.

head []
-- None

filter :: forall a. (a -> Bool) -> List a -> List a

Retain elements that satisfy the predicate, in their original order.