(* fetching lhs functions names *)
Definition lhs_func (r:rule):= (* => Syntax.v ? *)
  match r with
  | rule_intro f _ _ => f
  end.Definition all_lhs_funcs x := map lhs_func (rules x).

Lemma lhs_get_rules trsl: map lhs_func (get_rules trsl) = flat_map all_lhs_funcs trsl.