X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Fmatita%2Fcontribs%2Flambdadelta%2Fground%2Farith%2Fnat_rplus_pplus.ma;h=f3ae67e31085b2d6043f19eed543a830ba0d58b1;hb=4939d8280cb3467cd8fa648b1cea04f74d71e8b7;hp=661da6d710797eb806bae547a8f5377b61f093e3;hpb=e6ef5581641345f1c5c72f3c8b6040a9c6e5aecb;p=helm.git

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 661da6d71..f3ae67e31 100644
--- 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