--- /dev/null
+open Format
+
+type t = string
+type level = int
+
+let loggers = [ "top-down-run"; "top-down-approx"; "result-set"; "level2-jit"; "res-jit"; "grammar"; "twopass";"transition" ]
+let active_loggers : (t, int) Hashtbl.t = Hashtbl.create 17
+
+let available () = loggers
+
+let is_logger s = List.mem s loggers
+let level s = try Hashtbl.find active_loggers s with Not_found -> 0
+let is_active s = Hashtbl.mem active_loggers s
+let activate s lvl = if not (is_active s) then Hashtbl.add active_loggers s lvl
+let deactivate s = Hashtbl.remove active_loggers s
+
+let logger_output = ref err_formatter
+let set_output f = logger_output := f
+
+let log t l s =
+ if l <= level t
+ then begin
+ fprintf !logger_output "%s: " t;
+ fprintf !logger_output "%s%!" s
+ end