(* COROLLARIES: OK *)

(* Specifications: *)
Theorem expo_eq_exds_orb :forall(m:fmap)(z t:dart),
inv_hmap m -> exd m z ->
(expo m z t <-> exds (Iter_orb m z) t).
Theorem expo1_eq_exds_orb :forall(m:fmap)(z t:dart),
inv_hmap m -> exd m z ->
(expo1 m z t <-> exds (Iter_orb m z) t).