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Some cleanups and documentation

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Dave Halter
2018-06-13 10:10:17 +02:00
parent ec186a78f8
commit 3bc82d112d
1 changed files with 19 additions and 8 deletions
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27
parso/pgen2/pgen.py
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@@ -175,7 +175,7 @@ class _GrammarParser():
a, z = self._parse_rhs() a, z = self._parse_rhs()
self._expect(token.NEWLINE) self._expect(token.NEWLINE)
#_dump_nfa(a, z) _dump_nfa(a, z)
dfa = _make_dfa(a, z) dfa = _make_dfa(a, z)
#_dump_dfa(self._current_rule_name, dfa) #_dump_dfa(self._current_rule_name, dfa)
# oldlen = len(dfa) # oldlen = len(dfa)
@@ -197,21 +197,24 @@ class _GrammarParser():
else: else:
aa = NFAState(self._current_rule_name) aa = NFAState(self._current_rule_name)
zz = NFAState(self._current_rule_name) zz = NFAState(self._current_rule_name)
aa.add_arc(a) while True:
z.add_arc(zz) # Add the possibility to go into the state of a and come back
while self.value == "|": # to finish.
self._gettoken()
a, z = self._parse_alt()
aa.add_arc(a) aa.add_arc(a)
z.add_arc(zz) z.add_arc(zz)
if self.value != "|":
break
self._gettoken()
a, z = self._parse_alt()
return aa, zz return aa, zz
def _parse_alt(self): def _parse_alt(self):
# items: item+ # items: item+
a, b = self._parse_item() a, b = self._parse_item()
while (self.value in ("(", "[") or while self.type in (token.NAME, token.STRING, token.LPAR, token.LSQB):
self.type in (token.NAME, token.STRING)):
c, d = self._parse_item() c, d = self._parse_item()
# Need to end on the next item.
b.add_arc(c) b.add_arc(c)
b = d b = d
return a, b return a, b
@@ -222,6 +225,8 @@ class _GrammarParser():
self._gettoken() self._gettoken()
a, z = self._parse_rhs() a, z = self._parse_rhs()
self._expect(token.RSQB) self._expect(token.RSQB)
# Make it also possible that there is no token and change the
# state.
a.add_arc(z) a.add_arc(z)
return a, z return a, z
else: else:
@@ -230,10 +235,13 @@ class _GrammarParser():
if value not in ("+", "*"): if value not in ("+", "*"):
return a, z return a, z
self._gettoken() self._gettoken()
# Make it clear that we can go back to the old state and repeat.
z.add_arc(a) z.add_arc(a)
if value == "+": if value == "+":
return a, z return a, z
else: else:
# The end state is the same as the beginning, nothing must
# change.
return a, a return a, a
def _parse_atom(self): def _parse_atom(self):
@@ -246,6 +254,7 @@ class _GrammarParser():
elif self.type in (token.NAME, token.STRING): elif self.type in (token.NAME, token.STRING):
a = NFAState(self._current_rule_name) a = NFAState(self._current_rule_name)
z = NFAState(self._current_rule_name) z = NFAState(self._current_rule_name)
# Make it clear that the state transition requires that value.
a.add_arc(z, self.value) a.add_arc(z, self.value)
self._gettoken() self._gettoken()
return a, z return a, z
@@ -390,6 +399,7 @@ def _make_dfa(start, finish):
state.add_arc(st, label) state.add_arc(st, label)
return states # List of DFAState instances; first one is start return states # List of DFAState instances; first one is start
def _dump_nfa(start, finish): def _dump_nfa(start, finish):
print("Dump of NFA for", start.from_rule) print("Dump of NFA for", start.from_rule)
todo = [start] todo = [start]
@@ -406,6 +416,7 @@ def _dump_nfa(start, finish):
else: else:
print(" %s -> %d" % (label, j)) print(" %s -> %d" % (label, j))
def _dump_dfa(name, dfa): def _dump_dfa(name, dfa):
print("Dump of DFA for", name) print("Dump of DFA for", name)
for i, state in enumerate(dfa): for i, state in enumerate(dfa):