class RegexEvaluator:
def __init__(self, regex_tree):
self._nfa = self._automaton_from_regex(regex_tree)
self._dfa = Automaton()
self._dfa.states.append(State({-1}))
self._dfa.set_start_state({-1})
def _automaton_from_regex(self, root):
leafs = root.leaf_nodes()
graph = Automaton()
graph.states.append(State(-1))
for leaf in leafs:
graph.states.append(State(leaf.id))
graph.set_start_state(-1)
for node in root.last():
graph.set_end_state(node.id)
if root.empty():
graph.set_end_state(-1)
for node in root.first():
graph.add_transition(-1, node.character, node.id)
for leaf in leafs:
for node in leaf.next():
graph.add_transition(leaf.id, node.character, node.id)
return graph
def evaluate(self, word):
current_state = self._dfa.state_by_id({-1})
for char in word:
if self._dfa.follow_once(current_state, char) is None:
following = set()
for nfa_id in current_state.id:
following |= self._nfa.follow_all(
self._nfa.state_by_id(nfa_id), char)
following = self._nfa.ids_from_states(following)
if self._dfa.state_by_id(following, True) is None:
self._dfa.states.append(State(following))
for id in following:
if self._nfa.is_end_state(id):
self._dfa.set_end_state(following)
break
self._dfa.add_transition(current_state.id, char, following)
current_state = self._dfa.follow_once(current_state, char)
return current_state in self._dfa.end_states
def draw_nfa(self, suffix=""):
self._nfa.generate_dot('graph_nfa' + suffix + '.png')
def draw_dfa(self, suffix=""):
self._dfa.generate_dot('graph_dfa' + suffix + '.png')
def _automaton_from_regex(self, root):
leafs = root.leaf_nodes()
graph = Automaton()
graph.states.append(State(-1))
for leaf in leafs:
graph.states.append(State(leaf.id))
graph.set_start_state(-1)
for node in root.last():
graph.set_end_state(node.id)
if root.empty():
graph.set_end_state(-1)
for node in root.first():
graph.add_transition(-1, node.character, node.id)
for leaf in leafs:
for node in leaf.next():
graph.add_transition(leaf.id, node.character, node.id)
return graph
