class Kleene::NFA

def add_transition(token, from_state, to_state)
  # # make sure states EITHER have a single outbound epsilon transition OR non-epsilon outbound transitions; they can't have both
  # if token == NFATransition::Epsilon
  #   # make sure from_state doesn't have any outbound non-epsilon transitions
  #   raise "Error: Non-epsilon transitions are already present on #{from_state.to_s}! States may EITHER have a single outbound epsilon transision OR have outbound non-epsilon transitions, but not both." if transitions_from(from_state).any? {|t| !t.epsilon? }
  # else
  #   # make sure from_state doesn't have any outbound epsilon transition
  #   raise "Error: Epsilon transitions are already present on #{from_state.to_s}! States may EITHER have a single outbound epsilon transision OR have outbound non-epsilon transitions, but not both." if transitions_from(from_state).any?(&:epsilon?)
  # end
  @alphabet << token      # alphabet is a set, so there will be no duplications
  @states << from_state
  @states << to_state
  new_transition = NFATransition.new(token, from_state, to_state)
  char_transition_map = @transitions[from_state] ||= Hash.new
  set_of_transisions = char_transition_map[token] ||= Set.new
  set_of_transisions << new_transition
  new_transition
end