(* démo si mapget power predta_coacc = true alors l'état est coaccessible *)

Lemma predta_coacc_reverse :
forall (n : nat) (d : preDTA) (a b : ad),
MapGet bool (power (Map bool) (predta_coacc d a) (map_mini state d) n) b =
Some true -> coacc d a b.