def is_parseable(self, with_manipulation=False):
pdg = DirectedGraph() #parse decision graph
for rule in self.rules:
a,b = rule.head, rule.tail[0]
pdg.add_vertex(a)
pdg.add_vertex(b)
pdg.add_edge(a,b)
if not with_manipulation:
if pdg.is_cyclic():
return False
for leaf in pdg.leaves():
if not leaf.is_terminal():
return False
return True
def try_removing_useless_rules(self):
gen_graph = DirectedGraph()
for rule in self.rules:
for symbol in rule.unique_symbols():
if not symbol.is_terminal():
gen_graph.add_vertex(symbol)
for symbol in rule.tail:
if not symbol.is_terminal():
gen_graph.add_edge(rule.head, symbol)
removed = []
for s in gen_graph.get_unreachable(self.start):
to_del = self.rules_by_head(s)
for rule in to_del:
i = self.index(rule)
removed.append(i)
if removed:
self.__assert_parent__()
removed.sort()
for i in reversed(removed):
del self.rules[i]
self.__commit_transform__(Unremove(removed))
return len(removed)
