X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=helm%2Fsoftware%2Fmatita%2Fcontribs%2Fng_assembly%2Ffreescale%2Fnat_lemmas.ma;h=72ceb6188e680d5c8f701a19432128645340bdd9;hb=9f580d9bf8f6ba6950b252f587166e95bc8fb1a8;hp=70b9bbbb90418046b7ec8fe8f7a5dc75ec06d288;hpb=f8830ea7f8b308241d73e558092089a24ab2f867;p=helm.git

diff --git a/helm/software/matita/contribs/ng_assembly/freescale/nat_lemmas.ma b/helm/software/matita/contribs/ng_assembly/freescale/nat_lemmas.ma
index 70b9bbbb9..72ceb6188 100644
--- a/helm/software/matita/contribs/ng_assembly/freescale/nat_lemmas.ma
+++ b/helm/software/matita/contribs/ng_assembly/freescale/nat_lemmas.ma
@@ -113,3 +113,53 @@ nlemma eqnat_to_eq : ∀n1,n2:nat.(eq_nat n1 n2 = true → n1 = n2).
           ##]
  ##]
 nqed.
+
+nlemma Sn_p_n_to_S_npn : ∀n1,n2.(S n1) + n2 = S (n1 + n2).
+ #n1;
+ nelim n1;
+ ##[ ##1: nnormalize; #n2; napply (refl_eq ??)
+ ##| ##2: #n; #H; #n2; nrewrite > (H n2);
+          ncases n in H:(%) ⊢ %;
+          ##[ ##1: nnormalize; #H; napply (refl_eq ??)
+          ##| ##2: #n3; nnormalize; #H; napply (refl_eq ??)
+          ##]
+ ##]
+nqed.
+
+nlemma n_p_Sn_to_S_npn : ∀n1,n2.n1 + (S n2) = S (n1 + n2).
+ #n1;
+ nelim n1;
+ ##[ ##1: nnormalize; #n2; napply (refl_eq ??)
+ ##| ##2: #n; #H; #n2;
+          nrewrite > (Sn_p_n_to_S_npn n (S n2));
+          nrewrite > (H n2);
+          napply (refl_eq ??)
+ ##]
+nqed.
+
+nlemma Opn_to_n : ∀n.O + n = n.
+ #n; nnormalize; napply (refl_eq ??).
+nqed.
+
+nlemma npO_to_n : ∀n.n + O = n.
+ #n;
+ nelim n;
+ ##[ ##1: nnormalize; napply (refl_eq ??)
+ ##| ##2: #n1; #H;
+          nrewrite > (Sn_p_n_to_S_npn n1 O); 
+          nrewrite > H;
+          napply (refl_eq ??)
+ ##]
+nqed.
+
+nlemma symmetric_plusnat : symmetricT nat nat plus.
+ #n1;
+ nelim n1;
+ ##[ ##1: #n2; nrewrite > (npO_to_n n2); nnormalize; napply (refl_eq ??)
+ ##| ##2: #n2; #H; #n3;
+          nrewrite > (Sn_p_n_to_S_npn n2 n3);
+          nrewrite > (n_p_Sn_to_S_npn n3 n2);
+          nrewrite > (H n3);
+          napply (refl_eq ??)
+ ##]
+nqed.