(* Isolated darts are fixpoints for the the closure:*)

(* Specifications: *)
Lemma fixpoint_cA_cA_1 :
forall (m:fmap)(k:dim)(z:dart), inv_qhmap m ->
exd m z -> ~succ m k z -> ~pred m k z ->
cA m k z = z /\ cA_1 m k z = z.