# Pgen imports
from . import grammar, token, tokenize
+
class PgenGrammar(grammar.Grammar):
pass
-class ParserGenerator(object):
+class ParserGenerator(object):
def __init__(self, filename, stream=None):
close_stream = None
if stream is None:
self.filename = filename
self.stream = stream
self.generator = tokenize.generate_tokens(stream.readline)
- self.gettoken() # Initialize lookahead
+ self.gettoken() # Initialize lookahead
self.dfas, self.startsymbol = self.parse()
if close_stream is not None:
close_stream()
- self.first = {} # map from symbol name to set of tokens
+ self.first = {} # map from symbol name to set of tokens
self.addfirstsets()
def make_grammar(self):
return ilabel
else:
# An operator (any non-numeric token)
- itoken = grammar.opmap[value] # Fails if unknown token
+ itoken = grammar.opmap[value] # Fails if unknown token
if itoken in c.tokens:
return c.tokens[itoken]
else:
for name in names:
if name not in self.first:
self.calcfirst(name)
- #print name, self.first[name].keys()
+ # print name, self.first[name].keys()
def calcfirst(self, name):
dfa = self.dfas[name]
- self.first[name] = None # dummy to detect left recursion
+ self.first[name] = None # dummy to detect left recursion
state = dfa[0]
totalset = {}
overlapcheck = {}
for label, itsfirst in overlapcheck.items():
for symbol in itsfirst:
if symbol in inverse:
- raise ValueError("rule %s is ambiguous; %s is in the"
- " first sets of %s as well as %s" %
- (name, symbol, label, inverse[symbol]))
+ raise ValueError(
+ "rule %s is ambiguous; %s is in the"
+ " first sets of %s as well as %s"
+ % (name, symbol, label, inverse[symbol])
+ )
inverse[symbol] = label
self.first[name] = totalset
self.expect(token.OP, ":")
a, z = self.parse_rhs()
self.expect(token.NEWLINE)
- #self.dump_nfa(name, a, z)
+ # self.dump_nfa(name, a, z)
dfa = self.make_dfa(a, z)
- #self.dump_dfa(name, dfa)
+ # self.dump_dfa(name, dfa)
oldlen = len(dfa)
self.simplify_dfa(dfa)
newlen = len(dfa)
dfas[name] = dfa
- #print name, oldlen, newlen
+ # print name, oldlen, newlen
if startsymbol is None:
startsymbol = name
return dfas, startsymbol
# values.
assert isinstance(start, NFAState)
assert isinstance(finish, NFAState)
+
def closure(state):
base = {}
addclosure(state, base)
return base
+
def addclosure(state, base):
assert isinstance(state, NFAState)
if state in base:
for label, next in state.arcs:
if label is None:
addclosure(next, base)
+
states = [DFAState(closure(start), finish)]
- for state in states: # NB states grows while we're iterating
+ for state in states: # NB states grows while we're iterating
arcs = {}
for nfastate in state.nfaset:
for label, next in nfastate.arcs:
st = DFAState(nfaset, finish)
states.append(st)
state.addarc(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(self, name, start, finish):
print("Dump of NFA for", name)
while changes:
changes = False
for i, state_i in enumerate(dfa):
- for j in range(i+1, len(dfa)):
+ for j in range(i + 1, len(dfa)):
state_j = dfa[j]
if state_i == state_j:
- #print " unify", i, j
+ # print " unify", i, j
del dfa[j]
for state in dfa:
state.unifystate(state_j, state_i)
def parse_alt(self):
# ALT: ITEM+
a, b = self.parse_item()
- while (self.value in ("(", "[") or
- self.type in (token.NAME, token.STRING)):
+ while self.value in ("(", "[") or self.type in (token.NAME, token.STRING):
c, d = self.parse_item()
b.addarc(c)
b = d
self.gettoken()
return a, z
else:
- self.raise_error("expected (...) or NAME or STRING, got %s/%s",
- self.type, self.value)
+ self.raise_error(
+ "expected (...) or NAME or STRING, got %s/%s", self.type, self.value
+ )
def expect(self, type, value=None):
if self.type != type or (value is not None and self.value != value):
- self.raise_error("expected %s/%s, got %s/%s",
- type, value, self.type, self.value)
+ self.raise_error(
+ "expected %s/%s, got %s/%s", type, value, self.type, self.value
+ )
value = self.value
self.gettoken()
return value
while tup[0] in (tokenize.COMMENT, tokenize.NL):
tup = next(self.generator)
self.type, self.value, self.begin, self.end, self.line = tup
- #print token.tok_name[self.type], repr(self.value)
+ # print token.tok_name[self.type], repr(self.value)
def raise_error(self, msg, *args):
if args:
msg = msg % args
except:
msg = " ".join([msg] + list(map(str, args)))
- raise SyntaxError(msg, (self.filename, self.end[0],
- self.end[1], self.line))
+ raise SyntaxError(msg, (self.filename, self.end[0], self.end[1], self.line))
-class NFAState(object):
+class NFAState(object):
def __init__(self):
- self.arcs = [] # list of (label, NFAState) pairs
+ self.arcs = [] # list of (label, NFAState) pairs
def addarc(self, next, label=None):
assert label is None or isinstance(label, str)
assert isinstance(next, NFAState)
self.arcs.append((label, next))
-class DFAState(object):
+class DFAState(object):
def __init__(self, nfaset, final):
assert isinstance(nfaset, dict)
assert isinstance(next(iter(nfaset)), NFAState)
assert isinstance(final, NFAState)
self.nfaset = nfaset
self.isfinal = final in nfaset
- self.arcs = {} # map from label to DFAState
+ self.arcs = {} # map from label to DFAState
def addarc(self, next, label):
assert isinstance(label, str)
return False
return True
- __hash__ = None # For Py3 compatibility.
+ __hash__ = None # For Py3 compatibility.
+
def generate_grammar(filename="Grammar.txt"):
p = ParserGenerator(filename)
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