Section ListProperties.
Variable  X : Type.
Variables x y : X.
Variables l l1 l2 l3 : list X.

Lemma binds_app_uniq_iff :
uniq (E ++ F) ->
(binds x a (E ++ F) <->
(binds x a E /\ ~ In x (dom F)) \/
(binds x a F /\ ~ In x (dom E))).