(* OK: BUT REPLACE  betweenf m x_1 z x0 BY expf m x_1 z, WHICH IS EQUIVALENT: *)

Lemma between_expf_L0_3:forall (m:fmap)(x y:dart)(i:nat),
inv_hmap (L m zero x y) ->
let x0 := cA m zero x in
let x_1 := cA_1 m one x in
let z := Iter (cF m) i x_1 in
~ expf m x_1 y ->
betweenf m x_1 z x0 ->
expf (L m zero x y) x_1 z.