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_3 : forall s, of_list (to_list s) [=] s.