Hint Constructors PPO.

(* Specifications: *)
Lemma same_rank_same_ppo vv ff cc (t : term vv ff cc) s rk rk':
(forall f, In f (functions_of_term t) -> rk f = rk' f) ->
(forall f, In f (functions_of_term s) -> rk f = rk' f) ->
PPO rk t s -> PPO rk' t s.
Lemma same_rank_same_ppo_rule vv ff cc f lp (t : term vv ff cc) rk rk':
rk f = rk' f ->
(forall g, g ∈ (functions_of_term t) -> rk g = rk' g) ->
PPO rk t (fapply f (map (@term_from_pattern _ _ _) lp)) ->
PPO rk' t (fapply f (map (@term_from_pattern _ _ _) lp)).