(*========================================================= A AND A_1 ARE INVERSE INJECTIONS IN A qhmap: ==========================================================*)
(* In a qmap, A et A_1 are inverses of each other: *)

Lemma A_A_1 :
forall (m:fmap)(k:dim)(x y:dart),
inv_qhmap m -> exd m x -> exd m y
-> y = A m k x -> x = A_1 m k y.