(*s Computing the minimum of edges in a Map *)
Definition all_min (f : ad -> D -> option D) := MapFold _ _ None Ddmin f.

Lemma all_min_le_1 :
forall (f : ad -> D -> option D) (m : Map D) (a : ad) (d : D),
MapGet _ m a = Some d -> Ddle (all_min f m) (f a d) = true.