X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Fmatita%2Fcontribs%2Flambdadelta%2Fground%2Farith%2Fnat_rplus_pplus.ma;h=661da6d710797eb806bae547a8f5377b61f093e3;hb=be152b5436a8e1e107684722be834dbe02196d53;hp=314a1fd1788c2fe971e1880904a38556fa62da6c;hpb=e0c91d8a4422da0b39aca790e5826dc8a617b303;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 314a1fd17..661da6d71 100644
--- a/matita/matita/contribs/lambdadelta/ground/arith/nat_rplus_pplus.ma
+++ b/matita/matita/contribs/lambdadelta/ground/arith/nat_rplus_pplus.ma
@@ -13,7 +13,7 @@
 (**************************************************************************)
 
 include "ground/arith/pnat_plus.ma".
-include "ground/arith/nat_rplus.ma".
+include "ground/arith/nat_rplus_succ.ma".
 
 (* RIGHT ADDITION FOR NON-NEGATIVE INTEGERS *********************************)
 
@@ -22,3 +22,10 @@ include "ground/arith/nat_rplus.ma".
 lemma nrplus_inj_dx (p) (q):
       p + q = p + ninj q.
 // qed.
+
+lemma nrplus_pplus_assoc (p,q:pnat) (n:nat):
+      (p+q)+n = p+(q+n).
+#p #q #n
+@(nat_ind_succ … n) -n // #n #IH
+<nrplus_succ_dx <nrplus_succ_dx <pplus_succ_dx //
+qed.