src/HOL/Tools/datatype_codegen.ML

--- a/src/HOL/Tools/datatype_codegen.ML	Mon Nov 27 23:48:10 2006 +0100
+++ b/src/HOL/Tools/datatype_codegen.ML	Tue Nov 28 00:35:18 2006 +0100
@@ -609,7 +609,7 @@
             then NONE else SOME (arity, (tyco, cs)))) insts;
       in
         thy
-        |> K ((not o null) arities) ? (
+        |> not (null arities) ? (
             f arities css
             #-> (fn defs =>
               ClassPackage.prove_instance_arity tac arities ("", []) defs