(* IDEM, SYMMETRIC: *)

Lemma A_1_L_B_top_bot_ter:forall(m:fmap)(k:dim)(x z:dart),
inv_hmap m -> succ m k x -> let k1:=dim_opp k in
A_1 (L (B m k x) k (top m k x) (bottom m k x)) k1 z =
A_1 m k1 z.