def test_construct_pda(self):
cfg = ContextFreeGrammar()
cfg.add_rule('S', 'aR')
cfg.add_rule('R', 'aRb')
cfg.add_rule('R', '!')
pda = cfg.construct_pda()
start_transitions = {'!': [(State.Loop, ['S', '$'], None)]}
loop_transitions = {
'!': [(State.Loop, ['a', 'R'], 'S'),
(State.Loop, ['a', 'R', 'b'], 'R'),
(State.Loop, None, 'R'),
(State.Accept, None, '$')],
'a': [(State.Loop, None, 'a')],
'b': [(State.Loop, None, 'b')]
}
assert_transitions = {State.Start: start_transitions,
State.Loop: loop_transitions}
self.assertEqual(assert_transitions, pda.transitions)
def test_simulate(self):
# First input file
cfg = ContextFreeGrammar()
cfg.add_rule('S', 'aSb')
cfg.add_rule('S', '!')
expr1 = 'ab'
expr2 = 'aabb'
expr3 = '!'
expr4 = 'aaaabbbb'
expr5 = 'ababa'
expr6 = 'bbaaa'
self.assertTrue(cfg.simulate(expr1))
self.assertTrue(cfg.simulate(expr2))
self.assertTrue(cfg.simulate(expr3))
self.assertTrue(cfg.simulate(expr4))
self.assertFalse(cfg.simulate(expr5))
self.assertFalse(cfg.simulate(expr6))
# Second input file
cfg = ContextFreeGrammar()
cfg.add_rule('S', 'a_N_tells_a_N_O')
cfg.add_rule('N', 'boy')
cfg.add_rule('N', 'girl')
cfg.add_rule('O', 'a_story')
cfg.add_rule('O', 'that_S')
expr1 = 'a_boy_tells_a_girl_a_story'
expr2 = 'a_boy_tells_a_girl_that_a_boy_tells_a_girl_a_story'
expr3 = 'a_girl_tells_a_boy_a_story'
expr4 = 'a_girl_tells_a_boy_that_a_boy_tells_a_girl_that'
expr5 = 'a_story_tells_a_boy_a_story'
expr6 = 'a_boy_tells_a_tells_a_boy_a_story'
self.assertTrue(cfg.simulate(expr1))
self.assertTrue(cfg.simulate(expr2))
self.assertTrue(cfg.simulate(expr3))
self.assertFalse(cfg.simulate(expr4))
self.assertFalse(cfg.simulate(expr5))
self.assertFalse(cfg.simulate(expr6))
# Third input file
cfg = ContextFreeGrammar()
cfg.add_rule('S', 'XY')
cfg.add_rule('X', 'AX')
cfg.add_rule('X', '!')
cfg.add_rule('A', 'a')
cfg.add_rule('Y', 'BY')
cfg.add_rule('Y', '!')
cfg.add_rule('B', 'b')
expr1 = 'a'
expr2 = 'b'
expr3 = 'aaaaaaaabbbbbbbbb'
expr4 = '!'
expr5 = 'bbbbbbbbbbbbbbbbbbbbbb'
expr6 = 'ababab'
self.assertTrue(cfg.simulate(expr1))
self.assertTrue(cfg.simulate(expr2))
self.assertTrue(cfg.simulate(expr3))
self.assertTrue(cfg.simulate(expr4))
self.assertTrue(cfg.simulate(expr5))
self.assertFalse(cfg.simulate(expr6))
