diff -r e9d14d58be3c -r daf561a83ba6 core_marking2/docdiff_test3.scala
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/core_marking2/docdiff_test3.scala	Mon Apr 11 23:55:27 2022 +0100
@@ -0,0 +1,15 @@
+
+import C2._
+
+val urban_list1 = List("a", "b", "b", "c", "d")
+val urban_list2 = List("d", "b", "d", "b", "d")
+
+assert(prod(urban_list1, urban_list2) == 7)
+assert(prod(urban_list1, urban_list1) == 7)
+assert(prod(urban_list2, urban_list2) == 13)
+
+
+val urban_listA = List("a", "b", "b", "c", "d")
+val urban_listB = List("1", "2", "3", "4", "5")
+
+assert(prod(urban_listA, urban_listB) == 0)