test2 = do
  x <- bin (tip 1, bin (tip 2, tip 3))
  y <- bin (tip 'A', tip 'B')
  return (x, y)
test2 = do
  x <- bin (tip 1, bin (tip 2, tip 3))
  y <- bin (tip 'A', tip 'B')
  return (x, y)
test2 = do
  x <- bin (tip 1, bin (tip 2, tip 3))
  y <- bin (tip 'A', tip 'B')
  return (x, y)