Prototype

template <typename DFA1, typename InputIterator1>
void add_word(DFA1 &a, InputIterator1 first, InputIterator1 last, 
              const DFA1::tag_type &t = DFA1::tag_type());

template <typename DFA2, typename InputIterator2>
void add_words(DFA2 &a, InputIterator2 start, InputIterator2 finish);