Complete below functions in Ocaml:

(* Append two lists *)

let rec append (l1 : 'a list) (l2: 'a list) : 'a list =

(* TODO, replace [] *)

[]

-

(* Return the part of list l beginning at istart and running through

the end of the list *)

let rec list_suffix (istart : int) (l : 'a list) : 'a list =

(* TODO, replace [] *)

[]

-

(* Merge sorted lists l1 and l2 based on cmp. The result is a sorted

list containing all elements from both l2 and l2. *)

let rec merge (cmp : 'a->'a->bool) (l1 : 'a list) (l2 : 'a list) : 'a list =

(* TODO, replace [] *)

[]