diff -r ff525a38dba9 -r 7a0935571a23 src/Pure/PIDE/command.ML
--- a/src/Pure/PIDE/command.ML	Wed Jul 10 23:30:10 2013 +0200
+++ b/src/Pure/PIDE/command.ML	Thu Jul 11 10:43:53 2013 +0200
@@ -18,6 +18,7 @@
   val exec_ids: exec option -> Document_ID.exec list
   val stable_eval: eval -> bool
   val stable_print: print -> bool
+  val same_eval: eval * eval -> bool
   val read: (unit -> theory) -> Token.T list -> Toplevel.transition
   val eval: (unit -> theory) -> Token.T list -> eval -> eval
   val print: bool -> string -> eval -> print list -> print list option
@@ -111,6 +112,9 @@
 fun stable_print ({exec_id, print_process, ...}: print) =
   stable_goals exec_id andalso memo_stable print_process;
 
+fun same_eval (eval: eval, eval': eval) =
+  #exec_id eval = #exec_id eval' andalso stable_eval eval';
+
 
 (* read *)