(*========================================================= nf / LL : FOR L0L0: OK, COMPLETE IDEM FOR L0L1 (SET AS AXIOM) (TO COMPLETE) ==========================================================*)
(* OK, FOR nf_L0L0: *)

Lemma inv_hmap_L0L0:forall (m:fmap)(x y x' y':dart),
let m1:= L (L m zero x y) zero x' y' in
let m2:= L (L m zero x' y') zero x y in
inv_hmap m1 -> inv_hmap m2.