(* OK: *)

Lemma Iter_f_L_B: forall(m:fmap)(k:dim)(x z:dart)(i:nat),
inv_hmap m -> succ m k x ->
let m0:= L (B m k x) k (top m k x) (bottom m k x) in
Iter (MF.f m0) i z =  Iter (MF.f m) i z.