def unmatched_close(self):
self.close_symbol_pos = self.pos - 1
self.error_msg = "'{en}' unmatched at position {pos}."
self.error_msg = self.error_msg.format(en=self.current_state,
pos=self.close_symbol_pos)
raise Reject()
def unmatched_open(self):
self.open_symbol_pos = self.top_frame.pos - 1
self.error_msg = "'{en}' unmatched at position {pos}."
self.error_msg = self.error_msg.format(en=self.top_frame.state,
pos=self.open_symbol_pos)
raise Reject()
def on_no_transition(self, s_name):
if self.accepting:
raise Accept()
if self._backtrack():
return
else:
self.on_exhausted()
raise Reject("Backtracking exhausted.")
def bad_match(self):
self.open_symbol_pos = self.top_frame.pos - 1
self.close_symbol_pos = self.pos - 1
self.error_msg = "'{st}' at position {pos1} matched with '{en}' at "\
"position {pos2}."
self.error_msg = self.error_msg.format(st=self.top_frame.state,
pos1=self.open_symbol_pos,
en=self.current_state,
pos2=self.close_symbol_pos)
raise Reject()
def on_no_transition(self, s_name):
"""
Handle the no_transition notification.
The on_no_transition handler is called when a state has no acceptable
transitions available.
Args:
s_name: is the name of the state being exited.
Derived classes implementing this handler should call
super().on_no_transition().
"""
if self.accepting:
raise Accept()
msg = "Cannot transition from state {st}"
raise Reject(msg.format(st=self.current_state))
def _run(self):
"""
Helper function for run.
This is the heart of run(), but without the exception handling. _run
can be called recursively, e.g. in pushdown automata.
"""
assert self._current_state, "Initial state not set."
self._enter()
while True:
try:
self._do_activity()
self._transition()
except Backtrack:
# TODO: Handle this without referencing backtracking.
if not self._backtrack():
self.on_exhausted()
raise Reject("Backtracking exhausted.")