diff -r 3acec8c93c4b -r a2ee4b11c976 progs/pow.scala
--- a/progs/pow.scala	Thu Oct 19 11:04:43 2017 +0100
+++ b/progs/pow.scala	Thu Oct 19 13:15:22 2017 +0100
@@ -23,3 +23,13 @@
 
 pow(C, 3)
 pow(C, 3).size                            // -> 15
+
+
+val A = Set("a", "b", "c", "d")
+pow(A, 4).size   
+
+val A = Set("a", "b", "c")
+pow(A, 5).size   
+
+val A = Set("a", "b", "")
+pow(A, 5).size