--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ex/natsum.thy	Sun Mar 27 16:43:06 1994 +0200
@@ -0,0 +1,13 @@
+(*  Title: 	HOL/ex/natsum.thy
+    ID:         $Id$
+    Author: 	Tobias Nipkow
+    Copyright   1994 TU Muenchen
+
+A summation operator. sum(f,n+1) is the sum of all f(i), i=0...n.
+*)
+
+NatSum = Arith +
+consts sum :: "[nat=>nat, nat] => nat"
+rules  sum_0   "sum(f,0) = 0"
+       sum_Suc "sum(f,Suc(n)) = f(n) + sum(f,n)"
+end