1 files changed, 24 insertions, 0 deletions
diff --git a/src/nbc/stopwatch.sml b/src/nbc/stopwatch.sml
new file mode 100644
index 0000000..43547ed
--- /dev/null
+++ b/src/nbc/stopwatch.sml
@@ -0,0 +1,24 @@
+signature STOPWATCH = sig
+	exception FinishWithoutStart
+	val start: string -> unit
+	val finish: unit -> unit
+end
+structure Stopwatch :> STOPWATCH = struct
+	exception FinishWithoutStart
+	local
+		val time = ref NONE
+	in
+		fun start doing = (
+			print (concat [doing, "..."])
+			; time := SOME (Time.now ())
+		)
+		fun finish () = case !time of
+			SOME t => (
+				print (concat [
+					" done in "
+					, Time.toString (Time.- (Time.now (), t))
+					, " seconds.\n"
+				]); time := NONE
+			) | NONE => raise FinishWithoutStart
+	end
+end