let rec mandelbrot cre cim zre zim its =
  let zre2 = zre *. zre in
  let zim2 = zim *. zim in
  if zre2 +. zim2 >= 4.0 then
    if its >= 32 then "·"
    else if its >= 16 then "*"
    else "#"
  else if its >= 1000000 then " "
  else mandelbrot cre cim (zre2 -. zim2 +. cre) (2.0 *. zre *. zim +. cim) (its + 1)
;;

for y = 19 downto -20 do
  let cim = (float y) /. 20.0 in
  for x = -40 to 39 do
    let cre = (float x) /. 40.0 -. 0.5 in
    print_string (mandelbrot cre cim 0.0 0.0 0);
  done;
  print_endline ""
done;;