code: def PERM_OP(tup, n, m):
      "tup - (a, b, t)"
      a, b, t = tup
      t = ((a >> n) ^ b) & m
      b = b ^ t
      a = a ^ (t << n)
      return (a, b, tf PERM_OP(tup, n, m):
      "tup - (a, b, t)"
      a, b, t = tup
      t = ((a >> n) ^ b) & m
      b = b ^ t
      a = a ^ (t << n)
      return (a, b, t)
docs: tup - (a, b, t)