(* IDEM (TO PROVE), SYMMETRIC: BUT REPLACE betweenf m y_0_1 z y BY expf m y z which is EQUIVALENT *)
(* NEW FORMULATION!! *)

Lemma between_expf_L0_4_prel: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 y_0 := cA_1 m zero y in
let y_0_1 := cA_1 m one y_0 in
let z := Iter (cF m) i y_0_1 in
~ expf m x_1 y ->
betweenf m y_0_1 z y ->
expf (L m zero x y) y_0_1 z.