(* OK:*)

Lemma expf_B0_CS_1_a:forall (m:fmap)(x z t:dart),
inv_hmap m -> succ m zero x ->
let x0 := cA m zero x in
let xb0 := bottom m zero x in
let x_1 := cA_1 m one x in
expf m x0 xb0 ->
(betweenf m x_1 z xb0 /\ betweenf m x_1 t xb0)
-> expf (B m zero x) z t.