proposition: Lemma In_alt : forall k l, In k l <-> exists e, InA eqk (k,e) l.
proof: Proof. firstorder. exists x; auto with smtcoq_array. induction H. destruct y. exists e; auto with smtcoq_array. destruct IHInA as [e H0]. exists e; auto with smtcoq_array. Qed.
imports: Bool OrderedType SMT_classes ProofIrrelevance