diff -r 663c2a9108d1 -r 4de31fdc0d67 testing2/danube_test3.scala
--- a/testing2/danube_test3.scala	Sun Nov 01 01:21:31 2020 +0000
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,56 +0,0 @@
-import CW7b._
-
-
-// first test 
-
-val ls1_urban = List(("1", "a"), ("2", "a"), ("1", "c"), ("2", "a"), ("1", "c"))
-
-val m_urban = groupById(ls1_urban, Map())
-
-assert(m_urban.getOrElse("1", Nil).count(_ == "c") == 2)
-assert(m_urban.getOrElse("1", Nil).count(_ == "a") == 1)
-assert(m_urban.getOrElse("2", Nil) == List("a", "a"))
-
-// second test
-
-def urban_gb(ratings: List[(String, String)]) = 
-  ratings.groupBy(_._1).view.mapValues(_.map(_._2).toSet).toMap 
-
-def urban_gb2(ratings: List[(String, String)]) = 
-  ratings.groupBy(_._1).view.mapValues(_.map(_._2)).toMap 
-
-def urban_ck(ratings: List[(String, String)]) =
-  urban_gb(ratings) == groupById(ratings, Map()).view.mapValues(_.toSet).toMap
-
-
-val ls2_urban = List(("1", "a"), ("1", "b"), ("2", "x"), ("3", "a"), ("2", "y"), ("3", "c"))
-
-assert(urban_ck(ls2_urban))
-
-// thrird test
-
-val ls3_urban = (1 to 1000).map(_.toString).toList
-val ls4_urban = ls3_urban zip ls3_urban.tail
-val ls5_urban = ls4_urban ::: ls4_urban.reverse
-
-assert(urban_ck(ls5_urban))
-
-
-/*
-import io.Source
-import scala.util._
-
-def urban_get_csv_file(name: String) : List[String] = {
-  val csv = Source.fromFile(name)
-  csv.mkString.split("\n").toList.drop(1)
-}
-
-def urban_process_ratings(lines: List[String]) : List[(String, String)] = {
-  for (cols <- lines.map(_.split(",").toList); 
-       if (cols(2).toFloat >= 4)) yield (cols(0), cols(1))  
-}
-
-val urban_ratings = urban_process_ratings(urban_get_csv_file("ratings.csv").take(1000))
-
-assert(urban_ck(urban_ratings))
-*/