Method: Kleene::DSL#with_err_dead_end!

Defined in:
lib/kleene/dsl.rb

#with_err_dead_end!(nfa, alphabet = nfa.alphabet) ⇒ Object

adds and error state to the NFA, create error transitions from all non-error states to the error state on any unhandled token. the error state doesn’t have any outbound transitions.



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# File 'lib/kleene/dsl.rb', line 89

def with_err_dead_end!(nfa, alphabet = nfa.alphabet)
  error_state = nfa.states.find(&:error?)
  return nfa if error_state

  error_state = State.new_error_state
  nfa.add_state(error_state)

  nfa.states.each do |state|
    unless state.error?
      tokens_on_outbound_transitions = nfa.transitions_from(state).map(&:token).to_set
      only_outbound_transition_is_epsilon_transition = tokens_on_outbound_transitions.size == 1 && tokens_on_outbound_transitions.first == NFATransition::Epsilon
      unless only_outbound_transition_is_epsilon_transition
        missing_tokens = (alphabet - Set[NFATransition::Epsilon]) - tokens_on_outbound_transitions
        missing_tokens.each do |token|
          nfa.add_transition(token, state, error_state)
        end
      end
    end
  end

  # remove the error state if it has no inbound or outbound transitions
  nfa.remove_state(error_state) if nfa.all_transitions.none? {|transition| transition.from == error_state || transition.to == error_state }

  nfa.set_regex_pattern("/#{nfa.regex_pattern}/DE")
end