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
