def test_left_recursion(self):
rec = lazy()
r = alt("R", seqn("Ra", rec, lit('a')), lit('b'))
rec.set_rule(r)
parser = Parser('b')
pn = parser.apply_rule(rec, 0)
print(pn)
def test_add(self):
g = Grammar()
r = alt("MyAlt", lit('a'), lit('b'))
g.add(r)
self.assertEqual(3, len(g.rules))
rec = lazy()
C = seqn("At", rec, lit('t'))
B = seqn("Cd", C, lit('d'))
A = alt("A", seqn("Br", B, lit('r')), eps())
rec.set_rule(A)
g.add(A)
self.assertEqual(11, len(g.rules))
g.set_nullables()
for r in g.rules.values():
print(r, r.is_nullable)
print("---")
g.set_left_recursives()
for r in g.rules.values():
print(r, r.is_left_recursive)
def test_non_left_recursion(self):
rec = lazy()
r = alt("R", seqn("aRb", lit('a'), rec, lit('b')), eps())
rec.set_rule(r)
r.remove_lazy_rules()
pn = r.apply("ab", 0, 0)
self.check(pn, True, 0, 2)
r.init_memos()
pn = r.apply("aabb", 0, 0)
self.check(pn, True, 0, 4)
r.init_memos()
pn = r.apply("aacbb", 0, 0)
self.check(pn, True, 0, 0)
def test_indirect_left_recursion(self):
rec = lazy()
C = seqn("At", rec, lit('t'))
B = seqn("Cd", C, lit('d'))
A = alt("Br|eps", seqn("Br", B, lit('r')), eps())
rec.set_rule(A)
g = Grammar()
g.add(A)
g.set_nullables()
g.set_left_recursives()
# A.remove_lazy_rules()
Rule.DEBUG = True
pn = A.apply("tdr", 0, 0)
self.check(pn, True, 0, 3)
def test_left_recursion(self):
rec = lazy()
r = alt("R", seqn("Ra", rec, lit('a')), lit('b'))
rec.set_rule(r)
r.remove_lazy_rules()
pn = r.apply("b", 0, 0)
self.check(pn, True, 0, 1)
r.init_memo()
pn = r.apply("bac", 0, 0)
self.check(pn, True, 0, 2)
r.init_memo()
pn = r.apply("baa", 0, 0)
self.check(pn, True, 0, 3)
r.init_memo()
pn = r.apply("baaac", 0, 0)
self.check(pn, True, 0, 4)
def test_alt(self):
pn = alt("MyAlt", lit('a'), lit('b')).apply("abcd", 0)
self.check(pn, True, 0, 1)
pn = alt("MyAlt", lit('a'), lit('b')).apply("abcd", 2)
self.check(pn, False, 2, 0)