src/Pure/library.scala

   def error_dialog = simple_dialog(JOptionPane.ERROR_MESSAGE, "Error") _
 
 
   /* timing */
 
-  def timeit[A](e: => A) =
+  def timeit[A](message: String)(e: => A) =
   {
     val start = System.currentTimeMillis()
     val result = Exn.capture(e)
     val stop = System.currentTimeMillis()
-    System.err.println((stop - start) + "ms elapsed time")
+    System.err.println(
+      (if (message.isEmpty) "" else message + " ") + (stop - start) + "ms elapsed time")
     Exn.release(result)
   }
 }