(* AND (MORE TECHNICAL), OK!!: *)

Lemma degree_L1_merge_aux: forall(m:fmap)(x y:dart)(n:nat),
let m1:= L m one x y in
let y0 := cA m zero y in
let MAX:= MF.degree m x + MF.degree m y0 in
inv_hmap m1 -> ~expf m x y0 -> 1 <= MAX - n ->
MF.degree_aux m1 x (MAX - n) =
MF.degree m x + MF.degree m y0.