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Calculate the first plans in a very messy way

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Dave Halter
2018-06-21 21:10:28 +02:00
parent d8554d86d1
commit 31aecf2d35
1 changed files with 13 additions and 3 deletions
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16
parso/pgen2/grammar.py
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@@ -96,6 +96,7 @@ class Grammar(object):
def _make_grammar(self):
# Map from grammar rule (nonterminal) name to a set of tokens.
self._first_terminals = {}
self._first_plans = {}
nonterminals = list(self._nonterminal_to_dfas.keys())
nonterminals.sort()
@@ -128,8 +129,8 @@ class Grammar(object):
dfa_state.ilabel_to_plan = plans = {}
for terminal_or_nonterminal, next_dfa in dfa_state.arcs.items():
if terminal_or_nonterminal in self.nonterminal2number:
for first in self._make_first(terminal_or_nonterminal):
plans[first] = None
for t, plan in self._first_plans[terminal_or_nonterminal].items():
plans[t] = plan
else:
ilabel = self._make_label(terminal_or_nonterminal)
plans[ilabel] = DFAPlan(next_dfa)
@@ -205,6 +206,7 @@ class Grammar(object):
def _calculate_first_terminals(self, nonterminal):
dfas = self._nonterminal_to_dfas[nonterminal]
self._first_terminals[nonterminal] = None # dummy to detect left recursion
self._first_plans[nonterminal] = {}
# We only need to check the first dfa. All the following ones are not
# interesting to find first terminals.
state = dfas[0]
@@ -213,7 +215,7 @@ class Grammar(object):
for nonterminal_or_string, next_ in state.arcs.items():
if nonterminal_or_string in self._nonterminal_to_dfas:
# It's a nonterminal and we have either a left recursion issue
# in the grammare or we have to recurse.
# in the grammar or we have to recurse.
try:
fset = self._first_terminals[nonterminal_or_string]
except KeyError:
@@ -224,10 +226,18 @@ class Grammar(object):
raise ValueError("left recursion for rule %r" % nonterminal)
totalset.update(fset)
overlapcheck[nonterminal_or_string] = fset
for t, plan in self._first_plans[nonterminal_or_string].items():
assert not self._first_plans[nonterminal].get(t)
self._first_plans[nonterminal][t] = DFAPlan(
plan.next_dfa,
[nonterminal_or_string] + plan.pushes
)
else:
# It's a string. We have finally found a possible first token.
totalset.add(nonterminal_or_string)
overlapcheck[nonterminal_or_string] = set([nonterminal_or_string])
self._first_plans[nonterminal][nonterminal_or_string] = DFAPlan(next_)
inverse = {}
for nonterminal_or_string, first_set in overlapcheck.items():