(* OK: MODIFIED BY ADDING exd m z: *)

Lemma expf_B0_CS_1_c_prel:forall (m:fmap)(x z:dart)(i:nat),
inv_hmap m -> succ m zero x -> exd m z ->
let x0 := cA m zero x in
let xb0 := bottom m zero x in
let x_1 := cA_1 m one x in
let t:= Iter (cF m) i z in
expf m x0 xb0 -> ~ expf m x_1 z
-> expf (B m zero x) z t.