Definition In_dec := List.In_dec dec.

(* Specifications: *)
Lemma incl_dec (l l':list A) : {incl l l'}+{~incl l l'}.
Lemma NoDup_dec (l:list A) : {NoDup l}+{~NoDup l}.
Lemma uniquify_map A B (d:decidable_eq B)(f:A->B)(l:list A) : exists l', NoDup (map f l') /\ incl (map f l) (map f l').
Lemma uniquify A (d:decidable_eq A)(l:list A) : exists l', NoDup l' /\ incl l l'.