(**************************************)
(* PART 1:  summing a lot of integers *)
(**************************************)

(* sum of 0..n *)
let rec sum (n:int) : int =
  if n > 0 then
    n + sum (n-1)
  else 
    0

(* summing integers differently *)
let sum2 (n: int) : int =
  let rec aux (n:int) (a:int) : int =
    if n > 0 then
      aux (n-1) (a+n)
    else a
  in
  aux n 0


(* testing *)
let big_int = 1000000
let win() = sum2 big_int
let lose() = sum big_int

(*******************************************)
(* PART 2:  summing a big list of integers *)
(*******************************************)   

(* sum of the contents of l *)
let rec sum_list (l:int list) : int =
  match l with 
      [] -> 0
    | hd::tail -> hd + sum_list tail

(* sum the list a different way *)
let sum_list2 (l:int list) : int =
  let rec aux (l:int list) (a:int) : int =
    match l with 
	[] -> a
      | hd::tail -> aux tail (a+hd)
  in
  aux l 0

(* testing *)

let make (n:int) : int list =
  let rec aux (n:int) (l:int list) =
    if n <= 0 then l
    else aux (n-1) (n::l)
  in
  aux n []

let big_list = make 1000000
let win2() = sum_list2 big_list
let lose2() = sum_list big_list