(* OK!: *)

Lemma expf_L0_CS:forall (m:fmap)(x y z t:dart),
inv_hmap (L m zero x y) -> exd m z ->
let x0 := cA m zero x in
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
(if expf_dec m x_1 y
then
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 m x_1 z /\ expf m z t
else
expf m x_1 z /\ expf m y t
\/ expf m x_1 t /\ expf m y z
\/ expf m z t)
-> expf (L m zero x y) z t.