void local fn BuildWindow
  CGRect  r = {0,0,640,400}
  long    i, j, bars = 8
  CGFloat gray, delta, y = 0.0, w = 80

  window 1, @"Grayscale Bars", r

  pen -1
  for j = 1 to 4
    delta = 1.0/(bars-1)
    if ( j mod 2 ) then gray = 0.0 else gray = 1.0 : delta = -delta
    r = fn CGRectMake( 0, y, w, 100 )
    for i = 1 to bars
      rect fill r, fn ColorWithWhite( gray, 1.0 )
      r.origin.x += w
      gray += delta
    next
    bars = bars << 1
    y += 100 : w = w/2
  next
end fn

fn BuildWindow

HandleEvents