--- a/progs/lecture3.scala	Thu May 17 12:52:33 2018 +0100
+++ b/progs/lecture3.scala	Mon Jun 11 14:48:18 2018 +0100
@@ -121,6 +121,16 @@
 // actually colors can be written with "object",
 // because they do not take any arguments
 
+abstract class Day
+case object Monday extends Day 
+case object Tuesday extends Day 
+case object Wednesday extends Day
+case object Thursday extends Day 
+case object Friday extends Day 
+case object Saturday extends Day
+case object Sunday extends Day 
+
+
 
 // ... a bit more useful: Roman Numerals