(* expf / B *)
(* ========== 1ST PART OF CS: CASE expf m x0 xb0 =========== *)
(* OK : *)

Lemma expf_B0_CS_1_a_prel1:forall (m:fmap)(x:dart)(i j:nat),
inv_hmap m -> succ m zero x ->
let x_1 := cA_1 m one x in
let p := MF.Iter_upb m x_1 in
let xb0 := bottom m zero x in
let z := Iter (cF m) i x_1 in
xb0 = Iter (cF m) j x_1 ->
(i <= j < p)%nat
-> expf (B m zero x) x_1 z.