--- a/progs/pow.scala	Fri Oct 25 17:23:23 2019 +0100
+++ b/progs/pow.scala	Sun Oct 27 11:16:09 2019 +0000
@@ -6,6 +6,12 @@
   case n => concat(A, pow(A, n- 1))
 }
 
+val A = Set("aa", "aaa")
+val B = Set("aaa", "aa")
+concat(A, B).size                     // -> 28 
+
+
+
 val A = Set("1", "2", "3", "")
 val B = Set("1", "2", "3", "4", "5", "6", "")
 concat(A, B).size                     // -> 28