Instance Inhabitant_hist_el : Inhabitant hashtable_hist_el := HGet 0 0.

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