(* CONTRAVARIANT FORM AND NC: *)

Lemma expf_not_expf_L0_CV:forall (m:fmap)(x y:dart),
inv_hmap (L m zero x y) ->
let x_1:= cA_1 m one x in
let x0 := cA m zero x in
expf (L m zero x y) y x0 ->
~expf m x_1 y.