(* Why isn't this automatic? *)
Instance zero_ord_preorder : RelationClasses.PreOrder zero_ord.Instance table_incl_preorder : RelationClasses.PreOrder table_incl.

Lemma filter_find_count : forall {A} (f : A -> bool) d l li (Hunique : NoDup li) (Hli : forall i, In i li -> f (Znth i l d) = true) (Hrest : forall i, ~In i li -> f (Znth i l d) = false), Zlength (filter f l) = Zlength li.