def urbanmain() = {
  import C2._

  val urban_list1 = List("a", "b", "b", "c", "d")
  val urban_list2 = List("d", "b", "d", "b", "d")

  assert(overlap(urban_list1, urban_list2) == 0.5384615384615384)
  assert(overlap(urban_list1, urban_list1) == 1.0)
  assert(overlap(urban_list2, urban_list2) == 1.0)
}