(* OK! *)

Lemma top_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
top m0 zero z =
if MA0.expo_dec m x z H then x
else top m zero z.