(* OK!: *)

Lemma between_expf_L0_1:forall (m:fmap)(x y:dart)(i:nat),
inv_hmap (L m zero x y) ->
let x_1 := cA_1 m one x in
let z := Iter (cF m) i x_1 in
betweenf m x_1 z y ->
expf (L m zero x y) x_1 z.