def test_cat(self):
    a = NFA.build_a('a')
    b = NFA.build_a('b')
    ab = NFA.build_cat(a, b)

    self.assert_(ab.initial)
    self.assert_(ab.finals)
 def Cat(self, t):
   b = self.pop()
   a = self.pop()
   ab = NFA.build_cat(a, b)
   self.push(ab)