1 import M2 ._

     2 

     3 

     4 // first test 

     5 

     6 val ls1_urban = List(("1", "a"), ("2", "a"), ("1", "c"), ("2", "a"), ("1", "c"))

     7 

     8 val m_urban = groupById(ls1_urban, Map())

     9 

    10 assert(m_urban.getOrElse("1", Nil).count(_ == "c") == 2)

    11 assert(m_urban.getOrElse("1", Nil).count(_ == "a") == 1)

    12 assert(m_urban.getOrElse("2", Nil) == List("a", "a"))

    13 

    14 // second test

    15 

    16 def urban_gb(ratings: List[(String, String)]) = 

    17   ratings.groupBy(_._1).view.mapValues(_.map(_._2).toSet).toMap 

    18 

    19 def urban_gb2(ratings: List[(String, String)]) = 

    20   ratings.groupBy(_._1).view.mapValues(_.map(_._2)).toMap 

    21 

    22 def urban_ck(ratings: List[(String, String)]) =

    23   urban_gb(ratings) == groupById(ratings, Map()).view.mapValues(_.toSet).toMap

    24 

    25 

    26 val ls2_urban = List(("1", "a"), ("1", "b"), ("2", "x"), ("3", "a"), ("2", "y"), ("3", "c"))

    27 

    28 assert(urban_ck(ls2_urban))

    29 

    30 // thrird test

    31 

    32 val ls3_urban = (11 to 1000 by 5).map(_.toString).toList

    33 val ls4_urban = ls3_urban zip ls3_urban.tail

    34 val ls5_urban = ls4_urban ::: ls4_urban.reverse

    35 

    36 assert(urban_ck(ls5_urban))

    37 

    38 

    39 /*

    40 import io.Source

    41 import scala.util._

    42 

    43 def urban_get_csv_file(name: String) : List[String] = {

    44   val csv = Source.fromFile(name)

    45   csv.mkString.split("\n").toList.drop(1)

    46 }

    47 

    48 def urban_process_ratings(lines: List[String]) : List[(String, String)] = {

    49   for (cols <- lines.map(_.split(",").toList); 

    50        if (cols(2).toFloat >= 4)) yield (cols(0), cols(1))  

    51 }

    52 

    53 val urban_ratings = urban_process_ratings(urban_get_csv_file("ratings.csv").take(1000))

    54 

    55 assert(urban_ck(urban_ratings))

    56 */