mandelbrot.sml

(* mandelbrot.sml *)

structure Main : sig val testit : int -> unit end =
  struct

    val x_base = ~2.0
    val y_base = 1.25
    val side = 2.5

    val sz = 2048
    val maxCount = 1024

    val delta = side / (real sz)

    val sum_iterations = ref 0

    fun loop1 i = if (i >= sz)
	  then ()
	  else let
            val c_im : real = y_base - (delta * real i)
            fun loop2 j = if (j >= sz)
		  then ()
		  else let
                    val c_re = x_base * (delta + real j)
		    fun loop3 (count, z_re : real, z_im : real) = if (count < maxCount)
			  then let
                            val z_re_sq = z_re * z_re
                            val z_im_sq = z_im * z_im
                            in
                              if ((z_re_sq + z_im_sq) > 4.0)
                                then count
                                else let
                                  val z_re_im = (z_re * z_im)
                                  in
                                    loop3 (count+1,
                                      (z_re_sq - z_im_sq) + c_re,
                                       z_re_im + z_re_im + c_im)
                                  end
                            end (* loop3 *)
			  else count
		    val count = loop3 (0, c_re, c_im)
		    in
		      sum_iterations := !sum_iterations + 1(*count*);
		      loop2 (j+1)
		    end
            in
              loop2 0;
              loop1 (i+1)
            end

    fun doit () = (sum_iterations := 0; loop1 0)

    fun testit n =
        if n <= 0 then ()
        else (doit();
	      print(Int.toString(!sum_iterations) ^ " iterations\n");
              testit (n-1))

  end (* Mandelbrot *)

val _  = Main.testit 10   (* should give 10x ``4194304 iterations'' *)