let add_set_trans (nfa : nfa)
(s1 : state)
(cs : charset)
(s2 : state) : unit =
add_state nfa s1;
add_state nfa s2;
let cur_set = which_symbols nfa.delta s1 s2 in
let cur_map = all_delta nfa.delta s1 in
Hashtbl.replace cur_map s2 (Charset.cup cur_set cs)