--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Attic/danube_test4.scala	Sat Mar 11 22:01:53 2023 +0000
@@ -0,0 +1,29 @@
+
+// first test 
+
+import M2._
+
+def urban_groupById(ratings: List[(String, String)]) = 
+  ratings.groupBy(_._1).view.mapValues(_.map(_._2)).toMap 
+
+def urban_get_csv_file(name: String) : List[String] = {
+  import io.Source
+  import scala.util._
+  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_good_ratings = process_ratings(urban_get_csv_file("ratings.csv"))
+
+val urban_ratings_map = urban_groupById(urban_good_ratings)
+
+assert(favourites(urban_ratings_map, "912").length  == 80)
+assert(favourites(urban_ratings_map, "858").length  == 158)
+assert(favourites(urban_ratings_map, "260").length  == 201)
+