ceph/src/civetweb/src/third_party/duktape-1.8.0/examples/coffee/mandel.coffee

   1 mandel = (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
  27 mandel(-2, 2, 2, -2, 200, 100, 1000)
  28