diff -r 6a77c260c8a5 -r ac79c2e534bd core_testing2/docdiff_test4.scala
--- a/core_testing2/docdiff_test4.scala	Thu Nov 02 11:32:10 2023 +0000
+++ b/core_testing2/docdiff_test4.scala	Thu Nov 02 12:37:58 2023 +0000
@@ -1,11 +1,12 @@
 
-import C2._
 
-val urban_list1 = List("a", "b", "b", "c", "d")
-val urban_list2 = List("d", "b", "d", "b", "d")
+def urbanmain() = {
+  import C2._
 
-assert(overlap(urban_list1, urban_list2) == 0.5384615384615384)
+  val urban_list1 = List("a", "b", "b", "c", "d")
+  val urban_list2 = List("d", "b", "d", "b", "d")
 
-assert(overlap(urban_list1, urban_list1) == 1.0)
-
-assert(overlap(urban_list2, urban_list2) == 1.0)
+  assert(overlap(urban_list1, urban_list2) == 0.5384615384615384)
+  assert(overlap(urban_list1, urban_list1) == 1.0)
+  assert(overlap(urban_list2, urban_list2) == 1.0)
+}