def _check_for_input_rejection(self, current_state, stack):
"""Raise an error if the given config indicates rejected input."""
# If current state is not a final state and stack is not empty
if current_state not in self.final_states and stack:
raise exceptions.RejectionError(
'the DPDA stopped in a non-accepting configuration '
'({}, {})'.format(current_state, ''.join(stack)))
def _get_transition(self, state, tape_symbol):
"""Get the transiton tuple for the given state and tape symbol."""
if (state in self.transitions
and tape_symbol in self.transitions[state]):
return self.transitions[state][tape_symbol]
else:
raise exceptions.RejectionError(
'The machine entered a non-final configuration for which no '
'transition is defined ({}, {})'.format(state, tape_symbol))
def _get_next_current_state(self, current_state, input_symbol):
"""
Follow the transition for the given input symbol on the current state.
Raise an error if the transition does not exist.
"""
if input_symbol in self.transitions[current_state]:
return self.transitions[current_state][input_symbol]
else:
raise exceptions.RejectionError(
'{} is not a valid input symbol'.format(input_symbol))
def _get_transition(self, state, input_symbol, stack_symbol):
"""Get the transiton tuple for the given state and symbols."""
if (state in self.transitions
and input_symbol in self.transitions[state]
and stack_symbol in self.transitions[state][input_symbol]):
return self.transitions[state][input_symbol][stack_symbol]
else:
raise exceptions.RejectionError(
'The automaton entered a configuration for which no '
'transition is defined ({}, {}, {})'.format(
state, input_symbol, stack_symbol))
def _check_for_input_rejection(self, current_state):
"""Raise an error if the given config indicates rejected input."""
if current_state not in self.final_states:
raise exceptions.RejectionError(
'the DFA stopped on a non-final state ({})'.format(
current_state))
def _check_for_input_rejection(self, current_states):
"""Raise an error if the given config indicates rejected input."""
if not (current_states & self.final_states):
raise exceptions.RejectionError(
'the NFA stopped on all non-final states ({})'.format(
', '.join(current_states)))