module type FUN_UTILS = sig
  val cons : 'a -> 'a list -> 'a list
  val pair : 'a -> 'b -> 'a * 'b
  val triple : 'a -> 'b -> 'c -> 'a * 'b * 'c
  val flip : ('a -> 'b -> 'c) -> ('b -> 'a -> 'c) 
  val o : ('b -> 'c) -> ('a -> 'b) -> ('a -> 'c) 
  val id : 'a -> 'a
end

module FunUtils : FUN_UTILS = struct

  let cons x xs = x :: xs

  let pair x y = (x , y)

  let triple x y z= (x , y, z)

  let flip f a b = f b a 

  (* function composition *)
  let o f g x = f (g x)

  (* identity function *)
  let id x = x


end