Definition MapsTo (k:key)(e:elt):= InA eqke (k,e).Definition In k m := exists e:elt, MapsTo k e m.Notation Sort := (sort ltk).Notation Inf := (lelistA ltk).

Lemma In_inv : forall k k' e l, In k ((k',e) :: l) -> eq k k' \/ In k l.