Definition PMap_eq {A} (m m' : PMap.t (Z -> A)) := forall b' ofs', m !! b' ofs' = m' !! b' ofs'.

Lemma fold_right_rev_left:
forall (A B: Type) (f: A -> B -> A) (l: list B) (i: A),
fold_left f l i = fold_right (fun x y => f y x) i (rev l).