type level =
  | TRACE (* 0 *)
  | DEBUG (* 1 *)
  | INFO  (* 2 *)
  | WARN  (* 3 *)
  | ERROR (* 4 *)

external int_of_level : level -> int = "%identity"

type writer =
  timestamp:float ->
  namespace:string ->
  level:level ->
  string -> unit

let ( +++ ) w1 w2 ~timestamp ~namespace ~level msg =
  w1 ~timestamp ~namespace ~level msg;
  w2 ~timestamp ~namespace ~level msg