try to avoid races again (cf. 8c37cb84065f and fd3a36e48b09);
structure Report =
struct
local
val report_depth = Unsynchronized.ref 0
fun space n = if n <= 0 then "" else (space (n-1))^" "
fun report_space () = space (!report_depth)
in
fun timeit f =
let
val t1 = Timing.start ()
val x = f ()
val t2 = Timing.message (Timing.result t1)
val _ = writeln ((report_space ()) ^ "--> "^t2)
in
x
end
fun report s f =
let
val _ = writeln ((report_space ())^s)
val _ = report_depth := !report_depth + 1
val x = timeit f
val _ = report_depth := !report_depth - 1
in
x
end
end
end