src/Pure/Thy/thy_info.ML

 
 structure Presentation = Theory_Data
 (
   type T = ((presentation_context -> theory -> unit) * stamp) list;
   val empty = [];
-  val extend = I;
   fun merge data : T = Library.merge (eq_snd op =) data;
 );
 
 fun apply_presentation (context: presentation_context) thy =
   ignore (Par_List.map (fn (f, _) => f context thy) (Presentation.get thy));