マンデルブロ集合描くやつ

mandel.ml

#load "graphics.cma";;
let ( @. ) f g x = f (g x)

let rec natural acc = function
  | 0 -> acc
  | n -> natural (n :: acc) (n - 1)
let natural = natural []

let complex_of_pos (x, y) =
  (-1.5 +. float_of_int x *. 2. /. float_of_int (Graphics.size_x ()),
   -1. +.  float_of_int y *. 2. /. float_of_int (Graphics.size_y ()))

let rec is_mandel (re_z, im_z) n (re_c, im_c) = 
  if n = 0 then true
  else if re_z *. re_z +. im_z *. im_z > 4. then false
  else is_mandel
         (re_z *. re_z -. im_z *. im_z +. re_c, 2. *. re_z *. im_z +. im_c)
         (n - 1)
         (re_c, im_c)
let is_mandel = is_mandel (0., 0.)

let () = 
  Graphics.open_graph "";
  Graphics.resize_window 500 500;
  natural (Graphics.size_y ()) 
  |> List.map (fun i ->
      natural (Graphics.size_x ())
      |> List.map (fun j -> (i, j)))
  |> List.flatten
  |> List.filter (is_mandel 100 @. complex_of_pos)
  |> List.iter (fun (x, y) -> Graphics.plot x y)