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 = (1 to 1000).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 // fourth test !!!

    39 

    40 /*

    41  

    42 val ls6_urban = (10 to 500 by 10).map(_.toString).toList

    43 val ls7_urban = ls6_urban zip ls6_urban.tail

    44 val ls8_urban = ls7_urban ::: ls7_urban.reverse

    45 

    46 assert(urban_ck(ls8_urban)) 

    47 */