def __init__(self, formal_rule):
if not isinstance(formal_rule, str):
raise ValueError("rule constructor given %s; requires a string", type(formal_rule))
self.formal_rule = formal_rule
tokens = "(){}>,".split()
for token in tokens:
formal_rule = formal_rule.replace(token, " " + token + " ")
formal_rule = formal_rule.split()
self.from_const = constituent(formal_rule[0])
self.to_consts = map(lambda x: constituent(x), formal_rule[2:])
if formal_rule[1] != ">":
raise ValueError("Malformed rule: %s", formal_rule)
def gen_random_sentence(self, lexicon):
"""generate a random sentence according to this grammar using the
supplied lexicon
"""
tree = [constituent("S")]
while any(map(lambda x: x not in self.terminals, tree)):
next_tree = []
for const in tree:
if const in self.terminals:
next_tree.append(const)
else:
next_tree.extend(self.rules[const])
tree = next_tree
return " ".join(random.choice(lexicon.by_cat[x]) for x in tree)