(* cA_cA_1_B is defined *)
(* COROLLARIES : *)

Lemma cA_B : forall (m:fmap)(k:dim)(x z:dart),
inv_hmap m -> succ m k x ->
cA (B m k x) k z =
(if eq_dart_dec x z then bottom m k x
else if eq_dart_dec (top m k x) z then A m k x
else cA m k z).