(* OK!! *)

Lemma bottom_L_B_top_bot:
forall(m:fmap)(x z:dart)(H:inv_hmap m),
succ m zero x -> exd m z -> x <> z ->
let m0:= L (B m zero x)
zero (top m zero x) (bottom m zero x) in
bottom m0 zero z =
if MA0.expo_dec m x z H then (A m zero x)
else bottom m zero z.