open List

let rec foldl f x l =
  match l with
  | []     -> x
  | hd::tl -> foldl f (f x hd) tl
	
let rec foldr f x l =	
  match l with
  | []     -> x
  | hd::tl -> f hd (foldr f x tl)


let rec map f l =
  match l with
  | []     -> []
  | hd::tl -> (f hd)::(map f tl)

let rec iter f l =
  match l with
  | []     -> ()
  | hd::tl -> (f hd ; iter f tl)

let print_list f l =
  let fn x = (f x; print_string " ") in
    print_string "[ "; iter fn l; print_string "]"

let nl = print_newline