proposition: Lemma part_function_nth_strext : forall x y Hx Hy, F x Hx[^]n [#] F y Hy[^]n -> x [#] y.
proof: Proof. intros x y Hx Hy H. apply pfstrx with F Hx Hy. apply nexp_strext with n; assumption. Qed.
imports: CoRN.tactics.CornTac CoRN.algebra.CSums CoRN.algebra.CAbMonoids Coq.Sorting.Permutation CoRN.util.SetoidPermutation Coq.Setoids.Setoid Coq.Classes.Morphisms Coq(Lia)