X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Fmatita%2Fcontribs%2Flambdadelta%2Fground%2Farith%2Fnat_succ.ma;h=bb2300f021a2e549d6f25bbb13dd49ace62a07cc;hb=4d232392091ee233afc26ecf3120dd5f5c6a33c8;hp=916e6be1e5785f651c9208fc4c18c0a7ac236709;hpb=19b0a814861157ba05f23877d5cd94059f52c2e8;p=helm.git

diff --git a/matita/matita/contribs/lambdadelta/ground/arith/nat_succ.ma b/matita/matita/contribs/lambdadelta/ground/arith/nat_succ.ma
index 916e6be1e..bb2300f02 100644
--- a/matita/matita/contribs/lambdadelta/ground/arith/nat_succ.ma
+++ b/matita/matita/contribs/lambdadelta/ground/arith/nat_succ.ma
@@ -16,11 +16,19 @@ include "ground/arith/nat.ma".
 
 (* SUCCESSOR FOR NON-NEGATIVE INTEGERS **************************************)
 
-definition nsucc: nat → nat ≝ λm. match m with
-[ nzero  ⇒ ninj (𝟏)
-| ninj p ⇒ ninj (↑p)
+definition nsucc_pos (m): pnat ≝
+match m with
+[ nzero  ⇒ 𝟏
+| ninj p ⇒ ↑p
 ].
 
+interpretation
+  "positive successor (non-negative integers)"
+  'UpArrow m = (nsucc_pos m).
+
+definition nsucc (m): nat ≝
+           ninj (↑m).
+
 interpretation
   "successor (non-negative integers)"
   'UpArrow m = (nsucc m).
@@ -52,7 +60,7 @@ lemma nat_ind_2_succ (Q:relation2 …):
 #m #IH #n @(nat_ind_succ … n) -n /2 width=1 by/
 qed-.
 
-(* Basic inversions ***************************************************************)
+(* Basic inversions *********************************************************)
 
 (*** injective_S *)
 lemma eq_inv_nsucc_bi: injective … nsucc.