{- Returns `True` if the supplied function returns `True` for all elements in the `List` Examples: ``` ./all Natural Natural/even [ +2, +3, +5 ] = False ./all Natural Natural/even ([] : List Natural) = True ``` -} let all : ∀(a : Type) → (a → Bool) → List a → Bool = λ(a : Type) → λ(f : a → Bool) → λ(xs : List a) → List/fold a xs Bool (λ(x : a) → λ(r : Bool) → f x && r) True in all