update in ground

[helm.git] / matita / matita / contribs / lambdadelta / ground / arith / nat_rplus_pplus.ma

diff --git a/matita/matita/contribs/lambdadelta/ground/arith/nat_rplus_pplus.ma b/matita/matita/contribs/lambdadelta/ground/arith/nat_rplus_pplus.ma
index 661da6d710797eb806bae547a8f5377b61f093e3..f3ae67e31085b2d6043f19eed543a830ba0d58b1 100644 (file)
--- a/matita/matita/contribs/lambdadelta/ground/arith/nat_rplus_pplus.ma
+++ b/matita/matita/contribs/lambdadelta/ground/arith/nat_rplus_pplus.ma
@@ -13,6 +13,7 @@
 (**************************************************************************)
 
 include "ground/arith/pnat_plus.ma".
+include "ground/arith/nat_pred.ma".
 include "ground/arith/nat_rplus_succ.ma".
 
 (* RIGHT ADDITION FOR NON-NEGATIVE INTEGERS *********************************)
@@ -23,6 +24,11 @@ lemma nrplus_inj_dx (p) (q):
       p + q = p + ninj q.
 // qed.
 
+lemma nrplus_pnpred_dx (p) (q):
+      pnpred (p+q) = nrplus p (pnpred q).
+#p * //
+qed.
+
 lemma nrplus_pplus_assoc (p,q:pnat) (n:nat):
       (p+q)+n = p+(q+n).
 #p #q #n