(* THEN, OK: *)

Lemma between_expf_L0:forall (m:fmap)(x y z t:dart),
inv_hmap (L m zero x y) ->
let x_1 := cA_1 m one x in
let y_0_1 := cF m y in
let x0 := cA m zero x in
(betweenf m x_1 z y /\ betweenf m x_1 t y
\/ betweenf m y_0_1 z x0 /\ betweenf m y_0_1 t x0) ->
expf (L m zero x y) z t.