Xmas Tree in OCaml

xmas.ml

(* ocamlc unix.cma xmas.ml *)

type color = RST | RED | GRN | YEL | BLU | MAG | CYN | WHT

let rec mult_list n l = if n <= 0 then [] else l @ (mult_list (n-1) l)

let tree_elems =    (mult_list 5 [GRN, ">"; GRN, "<"]) @ 
                    [RED, "@"; BLU, "O"; MAG, "o"; YEL, "*"]
let snow_elems = (mult_list 15 [" "]) @ [".";",";"'";"*"]

let color_print c s =
    let colorcode = function
        | RST -> "0"
        | RED -> "31"
        | GRN -> "32"
        | YEL -> "33"
        | BLU -> "34"
        | MAG -> "35"
        | CYN -> "36"
        | WHT -> "37"
    in
    let color_str = "\x1B[1;" ^ (colorcode c) ^ "m"
    in
    print_string (color_str ^ s)

let color_reset () = color_print RST "\n"

let random_elem l = List.nth l (Random.int (List.length l))

let print_snow n =
    let rec snow_str n =
        if n <= 0 then ""
        else (random_elem snow_elems) ^ (snow_str (n-1))
    in color_print WHT (snow_str n)

let print_tree h sp =
    let rec random_level w = 
        if w <= 0 then ()
        else 
            let co, ch = random_elem tree_elems
            in
            color_print co ch; random_level (w-1)
    in
    let rec print_levels i = 
        if i <= 0 then () 
        else
        if i = h then (
            print_snow (i+sp);
            color_print YEL ("*");
            print_snow (i+sp);
            print_newline ();
            print_levels (i-1)
        )
        else (
            print_snow (i+sp);
            color_print GRN (">");
            random_level (2*(h-i)-1);
            color_print GRN ("<");
            print_snow (i+sp);
            print_newline ();
            print_levels (i-1)
        )
    in
    print_levels h;
    print_snow (h-1+sp);
    color_print WHT "| |";
    print_snow (h-1+sp);
    print_newline ();
    print_snow (h-3+sp);
    color_print WHT "__|_|__";
    print_snow (h-3+sp)

let save_int_of_string s d = 
    try
        int_of_string s
    with
        _ -> d

let get_term_size h w =
    let ic = Unix.open_process_in "stty size" in
    let out = Pervasives.input_line ic in
    match (String.split_on_char ' ' out) with
     | [nh; nw] -> save_int_of_string nh h, save_int_of_string nw w
     | _ -> h, w

let _ =
    Random.self_init ();
    let th, tw = get_term_size 40 80 in
    let w = tw-1 in
    let h = (min w th) - 20 in
    print_snow (w); print_newline ();
    print_snow (w); print_newline ();
    print_snow (w); print_newline ();
    print_snow (w); print_newline ();
    print_snow (w); print_newline ();
    print_tree h ((w-(h*2))/2);
    color_reset ()