def closure_1(grammar, state_set):
assert False
result = StateSet()
# Step 1
for state in state_set.elements:
result.add(state)
# Step 2
for state in result:
symbol = state.next_symbol()
if isinstance(symbol, Nonterminal):
f = set()
for l in state.lookahead:
betaL = []
betaL.extend(state.remaining_symbols())
betaL.append(l)
f |= old2_first(grammar, betaL)
alternatives = grammar[symbol].alternatives
for a in alternatives:
# create epsilon symbol if alternative is empty
if a == []:
a = [Epsilon()]
p = Production(symbol, a)
s = LR1Element(p, 0, f)
if a == [epsilon]:
s.d = 1
result.add(s)
# merge states that only differ in their lookahead
result.merge()
return result
def closure_1(grammar, state_set):
assert False
result = StateSet()
# Step 1
for state in state_set.elements:
result.add(state)
# Step 2
for state in result:
symbol = state.next_symbol()
if isinstance(symbol, Nonterminal):
f = set()
for l in state.lookahead:
betaL = []
betaL.extend(state.remaining_symbols())
betaL.append(l)
f |= old2_first(grammar, betaL)
alternatives = grammar[symbol].alternatives
for a in alternatives:
# create epsilon symbol if alternative is empty
if a == []:
a = [Epsilon()]
p = Production(symbol, a)
s = LR1Element(p, 0, f)
if a == [epsilon]:
s.d = 1
result.add(s)
# merge states that only differ in their lookahead
result.merge()
return result
