Lemma MapFold_Put_behind_disjoint_2 : forall (f:ad -> A -> M) (m:Map A) (a:ad) (y:A) (pf:ad -> ad), MapGet A m a = None -> MapFold1 A M neutral op f pf (MapPut_behind A m a y) = op (f (pf a) y) (MapFold1 A M neutral op f pf m).