milestone update in ground, partial commit

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

diff --git a/matita/matita/contribs/lambdadelta/ground/arith/nat_minus.ma b/matita/matita/contribs/lambdadelta/ground/arith/nat_minus.ma
index f386d413ae67a0c1f0b7bc72be7a2e4e5098006f..5d3726ca85c53b1dd16a30d5c7891079a3b51098 100644 (file)
--- a/matita/matita/contribs/lambdadelta/ground/arith/nat_minus.ma
+++ b/matita/matita/contribs/lambdadelta/ground/arith/nat_minus.ma
@@ -22,7 +22,7 @@ definition nminus: nat → nat → nat ≝
            λm,n. npred^n m.
 
 interpretation
-  "minus (positive integers)"
+  "minus (non-negative integers)"
   'minus m n = (nminus m n).
 
 (* Basic constructions ******************************************************)
@@ -70,6 +70,11 @@ lemma nminus_succ_sn_refl (m): ninj (𝟏) = ↑m - m.
 qed.
 
 (*** minus_minus_comm *)
-lemma nminus_minus_comm (o) (m) (n): o - m - n = o - n - m.
+lemma nminus_comm (o) (m) (n): o - m - n = o - n - m.
 #o #m #n @(nat_ind_succ … n) -n //
-qed-.
+qed.
+
+(*** minus_minus_comm3 *)
+lemma nminus_comm_231 (n) (m1) (m2) (m3):
+      n-m1-m2-m3 = n-m2-m3-m1.
+// qed.