dhall-1.42.3: dhall-lang/Prelude/List/head.dhall

--| Retrieve the first element of the list
let head
    : ∀(a : Type) → List a → Optional a
    = List/head

let example0 = assert : head Natural [ 0, 1, 2 ] ≡ Some 0

let example1 = assert : head Natural ([] : List Natural) ≡ None Natural

in  head