diff -r bdd731e4edbf -r b17a43f80ed0 progs/pow.scala
--- a/progs/pow.scala	Sat Nov 07 00:07:28 2020 +0000
+++ b/progs/pow.scala	Thu Nov 12 12:18:51 2020 +0000
@@ -6,6 +6,12 @@
   case n => concat(A, pow(A, n- 1))
 }
 
+val A = Set("a", "b", "c", "d", "e")
+val B = Set("a", "b", "c", "d", "")
+pow(A, 4).size
+pow(B, 4).size
+
+
 val A = Set("aa", "a")
 val B = Set("aaa", "aaaa")
 concat(A, B).size                     // -> 3