(* OUTSIDE x'ORBIT: *)

Lemma expf_not_orbit_x_aux:
forall (m:fmap)(x y z:dart)(i:nat),
inv_hmap (L m one x y) -> exd m z ->
let x1 := cA m one x in
let x10 := cA m zero x1 in
let y0 := cA m zero y in
let y_1 := cA_1 m one y in
let t:= Iter (cF m) i z in
expf m x y0 ->
~ expf m x z ->
expf (L m one x y) z t.