proposition: Lemma Inb_intro : forall x l, In x l -> Inb x l = true.
proof: Proof. induction l; simpl; intros. contr. case (eq_dec x a). auto. destruct H. intro. absurd (x = a); auto. auto. Qed.
imports: CoLoR(LogicUtil EqUtil RelUtil BoolUtil NatUtil) Coq(Setoid SetoidList FunInd)