Section BasicProperties.
Variable s s' s'' s1 s2 s3 : t.
Variable x x' : elt.
(** * Conversions between lists and sets *)
Definition of_list (l : list elt) := List.fold_right add empty l.
Definition to_list := elements.

Lemma of_list_2 : forall l, equivlistA E.eq (to_list (of_list l)) l.