diff -r 62eaaffe6e47 -r ddc965e172c4 src/Pure/Isar/local_theory.ML
--- a/src/Pure/Isar/local_theory.ML	Wed Apr 28 11:13:11 2010 +0200
+++ b/src/Pure/Isar/local_theory.ML	Wed Apr 28 11:41:27 2010 +0200
@@ -40,6 +40,7 @@
     local_theory -> (string * thm list) list * local_theory
   val declaration: bool -> declaration -> local_theory -> local_theory
   val syntax_declaration: bool -> declaration -> local_theory -> local_theory
+  val set_defsort: sort -> local_theory -> local_theory
   val type_notation: bool -> Syntax.mode -> (typ * mixfix) list -> local_theory -> local_theory
   val notation: bool -> Syntax.mode -> (term * mixfix) list -> local_theory -> local_theory
   val class_alias: binding -> class -> local_theory -> local_theory
@@ -183,7 +184,7 @@
 fun global_morphism lthy = standard_morphism lthy (ProofContext.init (ProofContext.theory_of lthy));
 
 
-(* basic operations *)
+(* primitive operations *)
 
 fun operation f lthy = f (#operations (get_lthy lthy)) lthy;
 fun operation1 f x = operation (fn ops => f ops x);
@@ -196,9 +197,16 @@
 val declaration = checkpoint ooo operation2 #declaration;
 val syntax_declaration = checkpoint ooo operation2 #syntax_declaration;
 
+
+
+(** basic derived operations **)
+
 val notes = notes_kind "";
 fun note (a, ths) = notes [(a, [(ths, [])])] #>> the_single;
 
+fun set_defsort S =
+  syntax_declaration false (K (Context.mapping (Sign.set_defsort S) (ProofContext.set_defsort S)));
+
 
 (* notation *)
 
@@ -224,6 +232,9 @@
 val const_alias = alias Sign.const_alias ProofContext.const_alias;
 
 
+
+(** init and exit **)
+
 (* init *)
 
 fun init group theory_prefix operations target =