proposition: Theorem inv_prop_l: forall a, In a isupport -> op (inv a) a = e.
proof: Proof. intros a H; unfold inv; apply inv_aux_prop_l with (l := support). change (is_inv a = true). apply isupport_is_inv_true; auto. Qed.
imports: ZArith Tactic Wf_nat UList ListAux FGroup