def test_is_factored():
g = ContextFreeGrammar.from_string('''
S -> a S | a B | d S
B -> b B | b
''')
assert not g.is_factored()
g = ContextFreeGrammar.from_string('''
S -> a S1 | d S
S1 -> S | B
B -> b B1
B1 -> B | &
''')
assert g.is_factored()
g = ContextFreeGrammar.from_string('''
S -> A B | B C
A -> a A | &
B -> b B | d
C -> c C | c
''')
assert not g.is_factored()
g = ContextFreeGrammar.from_string('''
S -> a A B | B C1
A -> a A | &
B -> b B | d
C -> c C1
C1 -> C | &
''')
assert g.is_factored()
def test_valid():
ContextFreeGrammar.from_string('E -> E + T | E - T | T\n'
'T -> T * F | T / F | F\n'
'F -> ( E ) | id')
ContextFreeGrammar.from_string('E -> T E1\n'
'E1 -> + T E1 | &\n'
'T -> F T1\n'
'T1 -> * F T1 | &\n'
'F -> ( E ) | id')
def test_invalid_spacing():
with raises(ParseError):
ContextFreeGrammar.from_string('E -> E+T | E-T | T\n'
'T -> T*F | T/F | F\n'
'F -> (E) | id')
with raises(ParseError):
ContextFreeGrammar.from_string('E -> T E1'
'E1 -> T E1 | &'
'T -> F T1'
'T1 -> * FT1 | &'
'F -> ( E ) | id')
def test_valid_with_whitespace():
ContextFreeGrammar.from_string('''
E -> E + T | E - T | T
T -> T * F | T / F | F
F -> ( E ) | id
''')
ContextFreeGrammar.from_string('''
E -> T E1
E1 -> + T E1 | &
T -> F T1
T1 -> * F T1 | &
F -> ( E ) | id
''')
def test_first_of_string():
string = '''S -> A B C
A -> a A | &
B -> b B | A C d
C -> c C | &'''
g = ContextFreeGrammar.from_string(string)
g.calculate_first()
expected = set({Terminal('c'), Terminal('d')})
got = g.first_of_string([NonTerminal('C'), Terminal('d')])
assert got == expected
def test_remove_simple_productions():
g = ContextFreeGrammar.from_string('''
S -> F G H
F -> G | a
G -> d G | H | b
H -> c
''')
expected = ContextFreeGrammar.from_string('''
S -> F G H
F -> a | d G | b | c
G -> d G | b | c
H -> c
''')
new_grammar = g.without_simple_productions()
new_productions = sorted(
(lhs, sorted(rhs))
for lhs, rhs in new_grammar.production_rules.items())
expected_productions = sorted(
(lhs, sorted(rhs)) for lhs, rhs in expected.production_rules.items())
assert new_productions == expected_productions
def test_n_sets():
g = ContextFreeGrammar.from_string('''
S -> F G H
F -> G | a
G -> d G | H | b
H -> c
''')
S, F, G, H = (NonTerminal(x) for x in 'SFGH')
expected = {
S: {S},
F: {F, G, H},
G: {G, H},
H: {H},
}
assert g.simple_production_sets() == expected
def test_first_nt_02():
S = NonTerminal('S')
A = NonTerminal('A')
B = NonTerminal('B')
epsilon = Epsilon('&')
string = '''S -> A b | A B c
B -> b B | A d | &
A -> a A | &'''
g = ContextFreeGrammar.from_string(string)
g.calculate_first_nt()
expected_first_nt = {
S: set([A, B]),
B: set([epsilon, A]),
A: set([epsilon]),
}
assert g.first_nt == expected_first_nt
def test_invalid_syntax():
with raises(ParseError):
ContextFreeGrammar.from_string('E + T | E - T | T\n'
'T -> T * F | T / F | F\n'
'F -> ( E ) | id')
with raises(ParseError):
ContextFreeGrammar.from_string('E -> T E1\n'
'E1 ->'
'T -> F T1\n'
'T1 -> * F T1 | &\n'
'F -> ( E ) | id')
with raises(ParseError):
ContextFreeGrammar.from_string('E -> E + T | E - T | T\n'
'T -> T * F | T / F |\n'
'F -> ( E ) | id')
with raises(ParseError):
ContextFreeGrammar.from_string('E -> T E1\n'
'E1 -> + T E1 | &\n'
'T -> F T1\n'
'T1 -> | &\n'
'F -> ( E ) | id')
def test_follow_02():
a = Terminal('a')
b = Terminal('b')
c = Terminal('c')
e = Terminal('e')
eos = EoS('$')
string = '''S -> A C | C e B | B a
A -> a A | B C
C -> c C | &
B -> b B | A B | &'''
g = ContextFreeGrammar.from_string(string)
g.calculate_follow()
expected_follow = {
NonTerminal('S'): set([eos]),
NonTerminal('A'): set([a, b, c, eos]),
NonTerminal('C'): set([a, b, c, e, eos]),
NonTerminal('B'): set([a, b, c, eos]),
}
assert g.follow == expected_follow
def test_follow_01():
a = Terminal('a')
b = Terminal('b')
c = Terminal('c')
d = Terminal('d')
eos = EoS('$')
string = '''S -> A B C
A -> a A | &
B -> b B | A C d
C -> c C | &'''
g = ContextFreeGrammar.from_string(string)
g.calculate_follow()
expected_follow = {
NonTerminal('S'): set([eos]),
NonTerminal('A'): set([a, b, c, d]),
NonTerminal('B'): set([c, eos]),
NonTerminal('C'): set([d, eos])
}
assert g.follow == expected_follow
def test_first_01():
a = Terminal('a')
b = Terminal('b')
c = Terminal('c')
d = Terminal('d')
epsilon = Epsilon('&')
string = '''S -> A B C
A -> a A | &
B -> b B | A C d
C -> c C | &'''
g = ContextFreeGrammar.from_string(string)
g.calculate_first()
expected_first = {
NonTerminal('S'): set([a, b, c, d]),
NonTerminal('A'): set([a, epsilon]),
NonTerminal('B'): set([a, b, c, d]),
NonTerminal('C'): set([c, epsilon])
}
assert g.first == expected_first
def test_first_02():
a = Terminal('a')
b = Terminal('b')
c = Terminal('c')
e = Terminal('e')
epsilon = Epsilon('&')
string = '''S -> A C | C e B | B a
A -> a A | B C
C -> c C | &
B -> b B | A B | &'''
g = ContextFreeGrammar.from_string(string)
g.calculate_first()
expected_first = {
NonTerminal('S'): set([a, b, c, e, epsilon]),
NonTerminal('A'): set([a, b, c, epsilon]),
NonTerminal('C'): set([c, epsilon]),
NonTerminal('B'): set([a, b, c, epsilon]),
}
assert g.first == expected_first
def test_first_nt_01():
S = NonTerminal('S')
A = NonTerminal('A')
B = NonTerminal('B')
C = NonTerminal('C')
epsilon = Epsilon('&')
string = '''S -> A B C
A -> a A | &
B -> b B | A C d
C -> c C | &'''
g = ContextFreeGrammar.from_string(string)
g.calculate_first_nt()
expected_first_nt = {
S: set([A, B, C]),
A: set([epsilon]),
B: set([A, C]),
C: set([epsilon]),
}
assert g.first_nt == expected_first_nt
from pprint import pprint
from chomchom import ContextFreeGrammar
g1 = ContextFreeGrammar.from_string('''
S -> a S1 | d S
S1 -> S | B
B -> b B1
B1 -> B | &
''')
g2 = ContextFreeGrammar.from_string('''
S -> A B | B C
A -> a A | &
B -> b B | d
C -> c C | c
''')
g3 = ContextFreeGrammar.from_string('''
S -> a S | B C | B D
A -> c C | A B
B -> b B | &
C -> a A | B C
D -> d D d | c
''')
# Empty grammar
g4 = ContextFreeGrammar.from_string('''
S -> a S
''')
g5 = ContextFreeGrammar.from_string('''