--| Transform a list by applying a function to each element
let map
    : ∀(a : Type) → ∀(b : Type) → (a → b) → List a → List b
    = λ(a : Type) →
      λ(b : Type) →
      λ(f : a → b) →
      λ(xs : List a) →
        List/build
          b
          ( λ(list : Type) →
            λ(cons : b → list → list) →
              List/fold a xs list (λ(x : a) → cons (f x))
          )

let example0 =
        assert
      : map Natural Bool Natural/even [ 2, 3, 5 ] ≡ [ True, False, False ]

let example1 =
        assert
      : map Natural Bool Natural/even ([] : List Natural) ≡ ([] : List Bool)

in  map