End Disjoint.
(* *********************************************************************** *)
(** * Basic facts about [uniq] *)
Section UniqProperties.
Variables A B   : Type.
Variables f     : A -> B.
Variables x     : atom.
Variables a b   : A.
Variables E F G : list (atom*A).

Axiom uniq_app_iff :
uniq (E ++ F) <-> uniq E /\ uniq F /\ disjoint E F.