(* i-SUCCS OF x BY cF_L1, FOR i < DEG OF x, ARE INVARIANT: *)

Lemma cF_L1_x_x10:forall(m:fmap)(x y:dart)(i:nat),
inv_hmap m -> prec_L m one x y ->
let y0 := cA m zero y in
let dx := MF.degree m x in
let m1:= L m one x y in
~expf m x y0 ->
i <= dx - 1 ->
Iter (cF m1) i x = Iter (cF m) i x.