let print l = 
    let rec aux l1 = match l1 with
          []    -> Printf.printf "[]";
        | h::[] -> Printf.printf "%d]" h
        | h::t  -> Printf.printf "%d; " h; aux t in
    Printf.printf "[";
    aux l;;

let print_ll ll =
    let rec aux l1 = match l1 with
          [] -> Printf.printf "[]";
        | h::[] -> print h; Printf.printf "]"
        | h::t -> print h; Printf.printf "; "; aux t in
    Printf.printf "[";
    aux ll;;

let flatten ll =
    let rec flat_out ol oa = match ol with
          []   -> oa
        | h::t -> flat_in h t oa
    and flat_in il ot ia = match il with
          []   -> flat_out ot ia
        | h::t -> flat_in t ot (h::ia) in
    List.rev (flat_out ll []);;

let interpolate l1 l2 =
    let rec inter x y a = match x,y with
          [],[]         -> a
        | [],h::t       -> inter t x (h::a)
        | h::t,[]       -> inter t y (h::a)
        | h1::t1,h2::t2 -> inter y t1 (h1::a) in
    List.rev (inter l1 l2 []);;

let range x m s =
    let rec aux c a = if c > m then a else aux (c + s) (c :: a) in
    List.rev (aux x []);;

let range_ll min max step division =
    let l = range min max step in
    let rec aux1 l1 a1 = match l1 with
          []   -> (List.rev a1)
        | h::t -> aux2 l1 0 [] a1
    and aux2 l2 len a2 a1 =
        if len < division
        then match l2 with
              []   -> aux2 [] division a2 a1
            | h::t -> aux2 t (len + 1) (h::a2) a1
        else aux1 l2 ((List.rev a2)::a1)
    in aux1 l [];;

let _ =
    let min = 1 and max = 5000000 in
    Printf.printf "Generating lists"; flush stdout;
    Printf.printf "."; flush stdout;
    let my_list = range min max 2 in
    Printf.printf "."; flush stdout;
    let my_other_list = range (min + 1) max 2 in
    Printf.printf "."; flush stdout;
    let my_list_list = range_ll min max 1 1 in
    Printf.printf "\n"; flush stdout;
    Printf.printf "\nMy List: "; flush stdout;
    (* print my_list; *)
    Printf.printf "\nMy Other List: "; flush stdout;
    (* print my_other_list; *)
    Printf.printf "\nMy List and My Other List Interpolated: "; flush stdout;
    (* print (interpolate my_list my_other_list); *)
    Printf.printf "\nMy List List: "; flush stdout;
    (* print_ll my_list_list; *)
    Printf.printf "\nMy List List Flattened: "; flush stdout;
    (* print (flatten my_list_list); *)
    Printf.printf "\n\n"; flush stdout;
    if (interpolate my_list my_other_list) = (flatten my_list_list)
    then (
        Printf.printf "The interpolated and flattened lists are equal!\n";
        flush stdout
    ) else (
        Printf.printf "Hmmm...\n";
        flush stdout
    );;