diff -r d63ec23c9125 -r 4a3c453f99a1 src/HOL/Int.thy
--- a/src/HOL/Int.thy	Wed Feb 20 12:04:42 2013 +0100
+++ b/src/HOL/Int.thy	Wed Feb 20 12:04:42 2013 +0100
@@ -303,6 +303,18 @@
 qed
 
 
+instance int :: no_top
+  apply default
+  apply (rule_tac x="x + 1" in exI)
+  apply simp
+  done
+
+instance int :: no_bot
+  apply default
+  apply (rule_tac x="x - 1" in exI)
+  apply simp
+  done
+
 subsection {* Magnitude of an Integer, as a Natural Number: @{text nat} *}
 
 lift_definition nat :: "int \<Rightarrow> nat" is "\<lambda>(x, y). x - y"