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[parser] Remove LR0 and SLR1

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Sorry, when this was educational it was nice to have the other
generators but as part of cleaning I'm just getting rid of them.
This commit is contained in:
John Doty 2024-10-15 07:43:52 -07:00
parent bb94fc6c9c
commit 2d5c73f0b0
2 changed files with 443 additions and 591 deletions
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117
tests/test_grammar.py
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@ -42,7 +42,7 @@ def test_lr0_lr0():
class G(Grammar):
start = "E"
generator = parser.GenerateLR0
# generator = parser.GenerateLR0
@rule
def E(self):
@ -86,7 +86,7 @@ def test_all_generators():
IDENTIFIER = Terminal("id", name="id")
GENERATORS = [
parser.GenerateLR0,
# parser.GenerateLR0,
parser.GeneratePager,
parser.GenerateLR1,
]
@ -104,121 +104,9 @@ def test_all_generators():
assert tree == _tree(("E", ("E", ("T", "id")), "+", ("T", "(", ("E", ("T", "id")), ")")))
def test_lr0_shift_reduce():
"""This one should not work in LR0- it has a shift/reduce conflict, but works in SLR1."""
class G(Grammar):
start = "E"
generator = parser.GenerateLR0
@rule
def E(self):
return seq(self.E, self.PLUS, self.T) | self.T
@rule
def T(self):
return (
seq(self.LPAREN, self.E, self.RPAREN)
| self.IDENTIFIER
| seq(self.IDENTIFIER, self.LSQUARE, self.E, self.RSQUARE)
)
PLUS = Terminal("+")
LPAREN = Terminal("(")
RPAREN = Terminal(")")
LSQUARE = Terminal("[")
RSQUARE = Terminal("]")
IDENTIFIER = Terminal("id")
with pytest.raises(parser.AmbiguityError):
G().build_table()
G().build_table(generator=parser.GenerateSLR1)
def test_lr0_reduce_reduce():
"""This one should not work, it has a reduce-reduce conflict."""
class G(Grammar):
start = "E"
generator = parser.GenerateLR0
@rule
def E(self):
return seq(self.E, self.PLUS, self.T) | self.T | seq(self.V, self.EQUAL, self.E)
@rule
def T(self):
return seq(self.LPAREN, self.E, self.RPAREN) | self.IDENTIFIER
@rule
def V(self):
return self.IDENTIFIER
PLUS = Terminal("+")
EQUAL = Terminal("=")
LPAREN = Terminal("(")
RPAREN = Terminal(")")
IDENTIFIER = Terminal("id")
with pytest.raises(parser.AmbiguityError):
G().build_table()
def test_lr0_empty():
"""LR0 can't handle empty productions because it doesn't know when to reduce."""
class G(Grammar):
start = "E"
generator = parser.GenerateLR0
@rule
def E(self):
return seq(self.F, self.BOOP)
@rule
def F(self):
return self.BEEP | parser.Nothing
BOOP = Terminal("boop")
BEEP = Terminal("beep")
with pytest.raises(parser.AmbiguityError):
G().build_table()
def test_grammar_aho_ullman_1():
class G(Grammar):
start = "S"
generator = parser.GenerateSLR1
@rule
def S(self):
return seq(self.L, self.EQUAL, self.R) | self.R
@rule
def L(self):
return seq(self.STAR, self.R) | self.ID
@rule
def R(self):
return self.L
EQUAL = Terminal("=")
STAR = Terminal("*")
ID = Terminal("id")
with pytest.raises(parser.AmbiguityError):
G().build_table()
G().build_table(generator=parser.GenerateLR1)
G().build_table(generator=parser.GeneratePager)
def test_grammar_aho_ullman_2():
class TestGrammar(Grammar):
start = "S"
generator = parser.GenerateSLR1
@rule
def S(self):
@ -231,7 +119,6 @@ def test_grammar_aho_ullman_2():
A = Terminal("a")
B = Terminal("b")
TestGrammar().build_table()
TestGrammar().build_table(generator=parser.GenerateLR1)
TestGrammar().build_table(generator=parser.GeneratePager)