(* OK: *)

Lemma cF_L1_y0:forall(m:fmap)(x y:dart),
inv_hmap m -> prec_L m one x y ->
let m1:= L m one x y in
let y0 := cA m zero y in
let dx := MF.degree m x in
let dy0 := MF.degree m y0 in
~expf m x y0 ->
Iter (cF m1) (dx + dy0) x = x.