Definition ad_list_of_dom :=
    MapFold A (list ad) nil (app (A:=ad)) (fun (a:ad) (_:A) => a :: nil).

Lemma ad_list_of_dom_card_1 : forall (m:Map A) (pf:ad -> ad), length (MapFold1 A (list ad) nil (app (A:=ad)) (fun (a:ad) (_:A) => a :: nil) pf m) = MapCard A m.