def test_expand1(self):
g = Lark("""start: a
?a: b
b: "x"
""")
r = g.parse('x')
self.assertEqual(r.children[0].data, "b")
g = Lark("""start: a
?a: b -> c
b: "x"
""")
r = g.parse('x')
self.assertEqual(r.children[0].data, "c")
g = Lark("""start: a
?a: B -> c
B: "x"
""")
self.assertEqual(r.children[0].data, "c")
g = Lark("""start: a
?a: b b -> c
b: "x"
""")
r = g.parse('xx')
self.assertEqual(r.children[0].data, "c")
def test_same_ast(self):
"Tests that Earley and LALR parsers produce equal trees"
g = Lark(r"""start: "(" name_list ("," "*" NAME)? ")"
name_list: NAME | name_list "," NAME
NAME: /\w+/ """,
parser='lalr')
l = g.parse('(a,b,c,*x)')
g = Lark(r"""start: "(" name_list ("," "*" NAME)? ")"
name_list: NAME | name_list "," NAME
NAME: /\w/+ """)
l2 = g.parse('(a,b,c,*x)')
assert l == l2, '%s != %s' % (l.pretty(), l2.pretty())
def test_earley_scanless2(self):
grammar = """
start: statement+
statement: "r"
| "c" /[a-z]/+
%ignore " "
"""
program = """c b r"""
l = Lark(grammar, parser='earley', lexer=LEXER)
l.parse(program)
def test_propagate_positions(self):
g = Lark("""start: a
a: "a"
""",
propagate_positions=True)
r = g.parse('a')
self.assertEqual(r.children[0].line, 1)
def test_earley_scanless(self):
g = Lark("""start: A "b" c
A: "a"+
c: "abc"
""",
parser="earley",
lexer=LEXER)
x = g.parse('aaaababc')
def test_earley_scanless4(self):
grammar = """
start: A A?
A: "a"+
"""
l = Lark(grammar, parser='earley', lexer=LEXER)
res = l.parse("aaa")
self.assertEqual(res.children, ['aaa'])
def test_anon_in_scanless(self):
# Fails an Earley implementation without special handling for empty rules,
# or re-processing of already completed rules.
g = Lark(r"""start: B
B: ("ab"|/[^b]/)*
""",
lexer=LEXER)
self.assertEqual(g.parse('abc').children[0], 'abc')
def test_earley_scanless3(self):
"Tests prioritization and disambiguation for pseudo-terminals (there should be only one result)"
grammar = """
start: A A
A: "a"+
"""
l = Lark(grammar, parser='earley', lexer=LEXER)
res = l.parse("aaa")
self.assertEqual(res.children, ['aa', 'a'])
def test_earley_repeating_empty(self):
# This was a sneaky bug!
grammar = """
!start: "a" empty empty "b"
empty: empty2
empty2:
"""
parser = Lark(grammar, parser='earley', lexer=LEXER)
res = parser.parse('ab')
empty_tree = Tree('empty', [Tree('empty2', [])])
self.assertSequenceEqual(res.children,
['a', empty_tree, empty_tree, 'b'])
def test_ambiguity1(self):
grammar = """
start: cd+ "e"
!cd: "c"
| "d"
| "cd"
"""
l = Lark(grammar,
parser='earley',
ambiguity='explicit',
lexer=LEXER)
x = l.parse('cde')
assert x.data == '_ambig', x
assert len(x.children) == 2
def test_earley_explicit_ambiguity(self):
# This was a sneaky bug!
grammar = """
start: a b | ab
a: "a"
b: "b"
ab: "ab"
"""
parser = Lark(grammar,
parser='earley',
lexer=LEXER,
ambiguity='explicit')
res = parser.parse('ab')
self.assertEqual(res.data, '_ambig')
self.assertEqual(len(res.children), 2)
def test_fruitflies_ambig(self):
grammar = """
start: noun verb noun -> simple
| noun verb "like" noun -> comparative
noun: adj? NOUN
verb: VERB
adj: ADJ
NOUN: "flies" | "bananas" | "fruit"
VERB: "like" | "flies"
ADJ: "fruit"
%import common.WS
%ignore WS
"""
parser = Lark(grammar, ambiguity='explicit', lexer=LEXER)
res = parser.parse('fruit flies like bananas')
expected = Tree('_ambig', [
Tree('comparative', [
Tree('noun', ['fruit']),
Tree('verb', ['flies']),
Tree('noun', ['bananas'])
]),
Tree('simple', [
Tree('noun', [Tree('adj', ['fruit']), 'flies']),
Tree('verb', ['like']),
Tree('noun', ['bananas'])
])
])
# print res.pretty()
# print expected.pretty()
self.assertEqual(res, expected)
def test_earley_prioritization_sum(self):
"Tests effect of priority on result"
grammar = """
start: ab_ b_ a_ | indirection
indirection: a_ bb_ a_
a_: "a"
b_: "b"
ab_: "ab"
bb_.1: "bb"
"""
l = _Lark(grammar, ambiguity='resolve__antiscore_sum')
res = l.parse('abba')
self.assertEqual(''.join(child.data for child in res.children),
'ab_b_a_')
grammar = """
start: ab_ b_ a_ | indirection
indirection: a_ bb_ a_
a_: "a"
b_: "b"
ab_.1: "ab"
bb_: "bb"
"""
l = Lark(grammar,
parser='earley',
ambiguity='resolve__antiscore_sum')
res = l.parse('abba')
self.assertEqual(''.join(child.data for child in res.children),
'indirection')
grammar = """
start: ab_ b_ a_ | indirection
indirection: a_ bb_ a_
a_.2: "a"
b_.1: "b"
ab_.3: "ab"
bb_.3: "bb"
"""
l = Lark(grammar,
parser='earley',
ambiguity='resolve__antiscore_sum')
res = l.parse('abba')
self.assertEqual(''.join(child.data for child in res.children),
'ab_b_a_')
grammar = """
start: ab_ b_ a_ | indirection
indirection: a_ bb_ a_
a_.1: "a"
b_.1: "b"
ab_.4: "ab"
bb_.3: "bb"
"""
l = Lark(grammar,
parser='earley',
ambiguity='resolve__antiscore_sum')
res = l.parse('abba')
self.assertEqual(''.join(child.data for child in res.children),
'indirection')
def test_embedded_transformer(self):
class T(Transformer):
def a(self, children):
return "<a>"
def b(self, children):
return "<b>"
def c(self, children):
return "<c>"
# Test regular
g = Lark("""start: a
a : "x"
""",
parser='lalr')
r = T().transform(g.parse("x"))
self.assertEqual(r.children, ["<a>"])
g = Lark("""start: a
a : "x"
""",
parser='lalr',
transformer=T())
r = g.parse("x")
self.assertEqual(r.children, ["<a>"])
# Test Expand1
g = Lark("""start: a
?a : b
b : "x"
""",
parser='lalr')
r = T().transform(g.parse("x"))
self.assertEqual(r.children, ["<b>"])
g = Lark("""start: a
?a : b
b : "x"
""",
parser='lalr',
transformer=T())
r = g.parse("x")
self.assertEqual(r.children, ["<b>"])
# Test Expand1 -> Alias
g = Lark("""start: a
?a : b b -> c
b : "x"
""",
parser='lalr')
r = T().transform(g.parse("xx"))
self.assertEqual(r.children, ["<c>"])
g = Lark("""start: a
?a : b b -> c
b : "x"
""",
parser='lalr',
transformer=T())
r = g.parse("xx")
self.assertEqual(r.children, ["<c>"])