--- a/progs/lecture4.scala	Tue Nov 12 00:41:00 2019 +0000
+++ b/progs/lecture4.scala	Tue Nov 12 10:47:27 2019 +0000
@@ -434,7 +434,7 @@
 // Conversions add a wrapper when a member of T is requested 
 // from an instance of C.
 
-//Another example
+//Another example (TimeUnit in 2.13?)
 
 case class Duration(time: Long, unit: TimeUnit) {
   def +(o: Duration) = Duration(time + unit.convert(o.time, o.unit), unit)