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Refactor out dfas

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Dave Halter
2018-06-13 00:31:45 +02:00
parent f8558df27a
commit f638abb08e
1 changed files with 23 additions and 22 deletions
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45
parso/pgen2/pgen.py
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@@ -181,7 +181,7 @@ class _GrammarParser():
dfa = self._make_dfa(a, z)
#self._dump_dfa(name, dfa)
# oldlen = len(dfa)
self._simplify_dfa(dfa)
_simplify_dfa(dfa)
# newlen = len(dfa)
dfas[name] = dfa
#print name, oldlen, newlen
@@ -251,27 +251,6 @@ class _GrammarParser():
for label, next in state.arcs.items():
print(" %s -> %d" % (label, dfa.index(next)))
def _simplify_dfa(self, dfa):
# This is not theoretically optimal, but works well enough.
# Algorithm: repeatedly look for two states that have the same
# set of arcs (same labels pointing to the same nodes) and
# unify them, until things stop changing.
# dfa is a list of DFAState instances
changes = True
while changes:
changes = False
for i, state_i in enumerate(dfa):
for j in range(i + 1, len(dfa)):
state_j = dfa[j]
if state_i == state_j:
#print " unify", i, j
del dfa[j]
for state in dfa:
state.unifystate(state_j, state_i)
changes = True
break
def _parse_rhs(self):
# rhs: items ('|' items)*
a, z = self._parse_alt()
@@ -408,6 +387,28 @@ class DFAState(object):
__hash__ = None # For Py3 compatibility.
def _simplify_dfa(dfas):
# This is not theoretically optimal, but works well enough.
# Algorithm: repeatedly look for two states that have the same
# set of arcs (same labels pointing to the same nodes) and
# unify them, until things stop changing.
# dfas is a list of DFAState instances
changes = True
while changes:
changes = False
for i, state_i in enumerate(dfas):
for j in range(i + 1, len(dfas)):
state_j = dfas[j]
if state_i == state_j:
#print " unify", i, j
del dfas[j]
for state in dfas:
state.unifystate(state_j, state_i)
changes = True
break
def generate_grammar(bnf_grammar, token_namespace):
"""
``bnf_text`` is a grammar in extended BNF (using * for repetition, + for