OCaml Code: Below is streams.ml and it needs the value "head". Please fix the code and make sure to test the code using various test cases to make sure the code works.  streams.ml let rec even n =   if n = 0 then true   else odd (n - 1) and odd n =   if n = 0 then false   else even (n - 1) let rec squares n =   let rec squares_aux m acc =     if m = 0 then List.rev acc     else squares_aux (m - 1) (acc @ [m * m])   in   squares_aux n []    let rec fibs n =   let rec fibs_aux a b count acc =     if count = 0 then List.rev acc     else fibs_aux b (a + b) (count - 1) (a :: acc)   in

OCaml Code: Below is streams.ml and it needs the value "head". Please fix the code and make sure to test the code using various test cases to make sure the code works. 

streams.ml

let rec even n =
  if n = 0 then true
  else odd (n - 1)
and odd n =
  if n = 0 then false
  else even (n - 1)

let rec squares n =
  let rec squares_aux m acc =
    if m = 0 then List.rev acc
    else squares_aux (m - 1) (acc @ [m * m])
  in
  squares_aux n []
  

let rec fibs n =
  let rec fibs_aux a b count acc =
    if count = 0 then List.rev acc
    else fibs_aux b (a + b) (count - 1) (a :: acc)
  in
  fibs_aux 0 1 n []

let rec evenFibs n =
  let rec fibs_aux a b count acc =
    if count = 0 then List.rev acc
    else if a mod 2 = 0 then fibs_aux b (a + b) (count - 1) (a :: acc)
    else fibs_aux b (a + b) count acc
  in
  fibs_aux 0 1 n []

let rec oddFibs n =
  let rec fibs_aux a b count acc =
    if count = 0 then List.rev acc
    else if a mod 2 = 1 then fibs_aux b (a + b) (count - 1) (a :: acc)
    else fibs_aux b (a + b) count acc
  in
  fibs_aux 1 1 n []

let rec is_prime n =
  let rec is_not_divisible k =
    k * k > n || (n mod k <> 0 && is_not_divisible (k + 1))
  in
  n > 1 && is_not_divisible 2

let rec primes n =
  let rec find_primes k count acc =
    if count = 0 then List.rev acc
    else if is_prime k then find_primes (k + 1) (count - 1) (k :: acc)
    else find_primes (k + 1) count acc
  in
  find_primes 2 n []

let rec rev_zip_diff l1 l2 f =
  match l1, l2 with
  | [], _ | _, [] -> []
  | x :: xs, y :: ys -> (x, y, f (x, y)) :: rev_zip_diff xs ys f

let rec printGenList lst f =
  match lst with
  | [] -> ()
  | x :: xs -> f x; printGenList xs f

let rec printList lst filename =
  let oc = open_out filename in
  let rec print_list_helper lst =
    match lst with
    | [] -> close_out oc
    | x :: xs -> output_string oc (string_of_int x ^ " "); print_list_helper xs
  in
  print_list_helper lst

let rec printPairList lst filename =
  let oc = open_out filename in
  let rec print_pair_list_helper lst =
    match lst with
    | [] -> close_out oc
    | (x, y) :: xs ->
        output_string oc ("(" ^ string_of_int x ^ ", " ^ string_of_int y ^ ") ");
        print_pair_list_helper xs
  in
  print_pair_list_helper lst

let rec take n lst =
  if n <= 0 then []
  else
    match lst with
    | [] -> []
    | x :: xs -> x :: take (n - 1) xs

let string_of_tuple_list lst =
  "[" ^ String.concat "; " (List.map (fun (x, y, z) -> "(" ^ string_of_int x ^ ", " ^ string_of_int y ^ ", " ^
                                                      string_of_int z ^ ")") lst) ^ "]"

let () =
  let string_of_int_list lst = "[" ^ String.concat "; " (List.map string_of_int lst) ^ "]" in

  print_endline ("even 2;;\n- : bool = " ^ string_of_bool (even 2));
  print_endline ("even 3;;\n- : bool = " ^ string_of_bool (even 3));
  print_endline ("odd 2;;\n- : bool = " ^ string_of_bool (odd 2));
  print_endline ("odd 3;;\n- : bool = " ^ string_of_bool (odd 3));
  print_endline ("take 10 squares;;\n- : int list = " ^ string_of_int_list (take 10 (squares 10)));
  print_endline ("take 10 fibs;;\n- : int list = " ^ string_of_int_list (take 10 (fibs 10)));
  print_endline ("take 10 evenFibs;;\n- : int list = " ^ string_of_int_list (take 10 (evenFibs 10)));
  print_endline ("take 10 oddFibs;;\n- : int list = " ^ string_of_int_list (take 10 (oddFibs 10)));
  print_endline ("take 10 primes;;\n- : int list = " ^ string_of_int_list (take 10 (primes 10)));
  print_endline ("take 5 (rev_zip_diff evenFibs oddFibs (fun (x,y)->x-y));;\n- : (int * int * int) list = " ^
                string_of_tuple_list (take 5 (rev_zip_diff (evenFibs 10) (oddFibs 10) (fun (x, y) -> x - y))));
  print_endline "printGenList [\"how\"; \"the\"; \"turntables\"] (fun s -> print_string (s ^ \" \"));;";
  printGenList ["how"; "the"; "turntables"] (fun s -> print_string (s ^ " "));
  print_endline "\n-: unit = ()";
  print_endline "printList [2; 4; 6; 8] \"printList.txt\";; (* \"2 4 6 8 \" *)";
  printList [2; 4; 6; 8] "printList.txt";
  print_endline "printPairList [(2, 1); (3, 2); (4, 3)] \"printPairList.txt\";; (* \"(2, 1) (3, 2) (4, 3) \" *)";
  printPairList [(2, 1); (3, 2); (4, 3)] "printPairList.txt"