let rec sumlist l =
	match l with
	| [] -> 0
	| h::t -> h + (sumlist t);;

let rec sumlist_tr_a l a =
	match l with
	| [] -> a
	| h::t -> sumlist_tr_a t (h + a);;

let sumlist_tr l =
	let rec helper l a =
	    match l with 
	    | [] -> a
	    | h::t -> helper t (h + a) in
	helper l 0;;

let rec makelist n =
	match n with
	| 0 -> []
	| _ -> n::(makelist (n - 1));;


let rec makelist_tr_a n a =
	match n with
	| 0 -> a
	| _ -> makelist_tr_a (n - 1) (n::a);;

let makelist_tr n =
	let rec helper n a =
	   match n with
	   | 0 -> a
	   | _ -> helper (n - 1) (n::a) in
	helper n [];;