// Test: Higher-order functions
let map = fn f list =>
  match list with
  | [] => []
  | x :: xs => f(x) :: map(f, xs)
  end

let filter = fn pred list =>
  match list with
  | [] => []
  | x :: xs =>
      if pred(x) then
        x :: filter(pred, xs)
      else
        filter(pred, xs)
  end

let main = fn () =>
  let numbers = [1, 2, 3, 4, 5] in
  let doubled = map(fn x => x * 2, numbers) in
  let evens = filter(fn x => x % 2 == 0, numbers) in
  print(doubled)