(* Fundamental theorem: (A m k) is a bijection on hmap support (exd m): *)

(* Specifications: *)
Theorem bij_A:
forall (m:fmap)(k:dim), inv_hmap m ->
bij_dart (exd m) (A m k).
Theorem bij_A_1:
forall (m:fmap)(k:dim), inv_hmap m ->
bij_dart (exd m) (A_1 m k).