Definition iteres_ult_const_def_0 (A : Set) (p : prechain A) : Prop :=
  forall (f : Map A -> Map A) (x : Map A) (n : nat),
  p = iteres A f x n ->
  non_dist_chain A p ->
  exists q : nat, S q <= n /\ power (Map A) f x q = power (Map A) f x (S q).

Lemma iteres_length : forall (A : Set) (f : Map A -> Map A) (x : Map A) (n : nat), chain_length A (iteres A f x n) = S n.