/usr/lib/pypy/dist-packages/rply/grammar.py is in pypy-rply 0.7.2-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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from rply.utils import iteritems
def rightmost_terminal(symbols, terminals):
for sym in reversed(symbols):
if sym in terminals:
return sym
return None
class Grammar(object):
def __init__(self, terminals):
# A list of all the productions
self.productions = [None]
# A dictionary mapping the names of non-terminals to a list of all
# productions of that nonterminal
self.prod_names = {}
# A dictionary mapping the names of terminals to a list of the rules
# where they are used
self.terminals = dict((t, []) for t in terminals)
self.terminals["error"] = []
# A dictionary mapping names of nonterminals to a list of rule numbers
# where they are used
self.nonterminals = {}
self.first = {}
self.follow = {}
self.precedence = {}
self.start = None
def add_production(self, prod_name, syms, func, precedence):
if prod_name in self.terminals:
raise ParserGeneratorError("Illegal rule name %r" % prod_name)
if precedence is None:
precname = rightmost_terminal(syms, self.terminals)
prod_prec = self.precedence.get(precname, ("right", 0))
else:
try:
prod_prec = self.precedence[precedence]
except KeyError:
raise ParserGeneratorError(
"Precedence %r doesn't exist" % precedence
)
pnumber = len(self.productions)
self.nonterminals.setdefault(prod_name, [])
for t in syms:
if t in self.terminals:
self.terminals[t].append(pnumber)
else:
self.nonterminals.setdefault(t, []).append(pnumber)
p = Production(pnumber, prod_name, syms, prod_prec, func)
self.productions.append(p)
self.prod_names.setdefault(prod_name, []).append(p)
def set_precedence(self, term, assoc, level):
if term in self.precedence:
raise ParserGeneratorError(
"Precedence already specified for %s" % term
)
if assoc not in ["left", "right", "nonassoc"]:
raise ParserGeneratorError(
"Precedence must be one of left, right, nonassoc; not %s" % (
assoc
)
)
self.precedence[term] = (assoc, level)
def set_start(self):
start = self.productions[1].name
self.productions[0] = Production(0, "S'", [start], ("right", 0), None)
self.nonterminals[start].append(0)
self.start = start
def unused_terminals(self):
return [
t
for t, prods in iteritems(self.terminals)
if not prods and t != "error"
]
def unused_productions(self):
return [p for p, prods in iteritems(self.nonterminals) if not prods]
def build_lritems(self):
"""
Walks the list of productions and builds a complete set of the LR
items.
"""
for p in self.productions:
lastlri = p
i = 0
lr_items = []
while True:
if i > p.getlength():
lri = None
else:
try:
before = p.prod[i - 1]
except IndexError:
before = None
try:
after = self.prod_names[p.prod[i]]
except (IndexError, KeyError):
after = []
lri = LRItem(p, i, before, after)
lastlri.lr_next = lri
if lri is None:
break
lr_items.append(lri)
lastlri = lri
i += 1
p.lr_items = lr_items
def _first(self, beta):
result = []
for x in beta:
x_produces_empty = False
for f in self.first[x]:
if f == "<empty>":
x_produces_empty = True
else:
if f not in result:
result.append(f)
if not x_produces_empty:
break
else:
result.append("<empty>")
return result
def compute_first(self):
for t in self.terminals:
self.first[t] = [t]
self.first["$end"] = ["$end"]
for n in self.nonterminals:
self.first[n] = []
changed = True
while changed:
changed = False
for n in self.nonterminals:
for p in self.prod_names[n]:
for f in self._first(p.prod):
if f not in self.first[n]:
self.first[n].append(f)
changed = True
def compute_follow(self):
for k in self.nonterminals:
self.follow[k] = []
start = self.start
self.follow[start] = ["$end"]
added = True
while added:
added = False
for p in self.productions[1:]:
for i, B in enumerate(p.prod):
if B in self.nonterminals:
fst = self._first(p.prod[i + 1:])
has_empty = False
for f in fst:
if f != "<empty>" and f not in self.follow[B]:
self.follow[B].append(f)
added = True
if f == "<empty>":
has_empty = True
if has_empty or i == (len(p.prod) - 1):
for f in self.follow[p.name]:
if f not in self.follow[B]:
self.follow[B].append(f)
added = True
class Production(object):
def __init__(self, num, name, prod, precedence, func):
self.name = name
self.prod = prod
self.number = num
self.func = func
self.prec = precedence
self.unique_syms = []
for s in self.prod:
if s not in self.unique_syms:
self.unique_syms.append(s)
self.lr_items = []
self.lr_next = None
self.lr0_added = 0
self.reduced = 0
def __repr__(self):
return "Production(%s -> %s)" % (self.name, " ".join(self.prod))
def getlength(self):
return len(self.prod)
class LRItem(object):
def __init__(self, p, n, before, after):
self.name = p.name
self.prod = p.prod[:]
self.prod.insert(n, ".")
self.number = p.number
self.lr_index = n
self.lookaheads = {}
self.unique_syms = p.unique_syms
self.lr_before = before
self.lr_after = after
def __repr__(self):
return "LRItem(%s -> %s)" % (self.name, " ".join(self.prod))
def getlength(self):
return len(self.prod)
|