fun map (f, l) {
  case l of
    Nil          -> Nil
  | Cons (h, tl) -> Cons (f (h), map (f, tl))
  esac
}

fun a (x) {x + 1}
fun b (x) {x + 2}

fun print_list (x) {
  case x of
    Nil          -> skip
  | Cons (h, tl) -> write (h); print_list (tl)
  esac
}

val x = read ();

print_list (Cons (1, Cons (2, Cons (3, Nil))));
print_list (map (a, Cons (1, Cons (2, Cons (3, Nil)))));
print_list (map (b, Cons (1, Cons (2, Cons (3, Nil)))))