src/Pure/ML/exn_properties_dummy.ML

allow more control of main loop;
more robust is_active test, although thread could terminate at any time;

(*  Title:      Pure/ML/exn_properties_dummy.ML
    Author:     Makarius

Exception properties -- dummy version.
*)

signature EXN_PROPERTIES =
sig
  val get: exn -> Properties.T
  val update: Properties.entry list -> exn -> exn
end;

structure Exn_Properties: EXN_PROPERTIES =
struct

fun get _ = [];
fun update _ exn = exn;

end;