--- a/progs/pow.scala	Fri Oct 12 10:16:54 2018 +0100
+++ b/progs/pow.scala	Sat Oct 13 13:51:28 2018 +0100
@@ -38,3 +38,13 @@
 
 for (n <- (0 to 6).toList) 
   yield pow(B, n).size
+
+
+
+
+
+val A = Set("a", "b", "c")
+pow(A, 3)
+
+val B = Set("a", "b", "")
+pow(B, 4)