Base theory is now Arith, not Nat. (because all datatypes now require Arith).

--- a/src/HOLCF/Porder0.thy	Fri May 23 09:18:06 1997 +0200
+++ b/src/HOLCF/Porder0.thy	Fri May 23 09:20:35 1997 +0200
@@ -7,11 +7,11 @@
 
 *)
 
-Porder0 = Nat +
+Porder0 = Arith +
 
 (* first the global constant for HOLCF type classes *)
 consts
-  "less"        :: "['a,'a] => bool"
+  less        :: "['a,'a] => bool"
 
 axclass po < term
         (* class axioms: *)