1mandel = (x0, y0, x1, y1, w, h, maxiter) ->
2  [dx, dy] = [(x1 - x0) / w, (y1 - y0) / h]
3  res = []
4
5  y = y0
6  for yc in [0..h-1]
7    x = x0
8    for xc in [0..w-1]
9      [xx, yy] = [x, y]
10      c = '*'
11      for i in [0..maxiter-1]
12        # (xx+i*yy)^2 + (x+i*y) = xx^2 + i*2*xx*yy - yy^2 + x + i*y
13        # = (xx^2 - yy^2 + x) + i*(2*xx*yy + y)
14        [xx2, yy2] = [xx*xx, yy*yy]
15        if xx2 + yy2 >= 4.0
16          c = '.'
17          break
18        [xx, yy] = [xx2 - yy2 + x, 2*xx*yy + y]
19      res.push(c)
20      x += dx
21    res.push('\n')
22    y += dy
23
24  print(res.join(''))
25  return
26
27mandel(-2, 2, 2, -2, 200, 100, 1000)
28
29