Scala collections: mapping letters example

numbers.scala

package week6

import scala.io.Source

object collections {
  /* read a file of words */
  val in = Source.fromURL("http://lamp.epfl.ch/files/content/sites/lamp/files/teaching/progfun/linuxwords.txt")
  
  /* create a list and filter all words where *all* their characters are not letters (like dashes) */
  val words = in.getLines.toList filter (word => word forall (chr => chr.isLetter))
  
  /* define the map of numbers to letters */
  val nmem = Map( '2' -> "ABC", '3' -> "DEF", '4' -> "GHI", '5' -> "JKL", '6' -> "MNO", '7' -> "PQRS", '8' -> "TUV", '9' -> "WXYZ")
  
  /* invert the map the get a map of letters to digits */
  val charCode: Map[Char, Char] = for ((digit, str) <- nmem; ltr <- str) yield ltr -> digit
  
  /* define a function that returns the numbers of a given word */
  def wordCode(word: String): String = word.toUpperCase map charCode
  
  /* group all words of our long list with the same number */
  val wordsForNum: Map[String, Seq[String]] = words groupBy wordCode withDefaultValue Seq()
  
  /* function that receives a number and finds the words that match it */
  def encode(number: String): Set[List[String]] =
    if (number.isEmpty) Set(List())
    else {
      for {
        split <- 1 to number.length // iterate over the number
        word <- wordsForNum(number take split) // get the word before the spilt
        rest <- encode(number drop split) //get the words after the split
      } yield word :: rest // join the results
    }.toSet // pass a set to the for              

  /* better print of the results */
  def translate(number: String): Set[String] = encode(number) map (_ mkString " ")           

  /* test the translate and print results*/
  translate("7225247386") foreach println         //> sack air fun
                                                  //| pack ah re to
                                                  //| pack bird to
                                                  //| Scala ire to
                                                  //| Scala is fun
                                                  //| rack ah re to
                                                  //| pack air fun
                                                  //| sack bird to
                                                  //| rack bird to
                                                  //| sack ah re to
                                                  //| rack air fun

}

It is not nmem, it is mnem which stands for "mnemonics". Your variables are named improperly.

do you really care?

gracias Jorge por tenerlo todo tan ordenadito :p

the link has been changed to https://lamp.epfl.ch/wp-content/uploads/2019/01/linuxwords.txt

Thanks a lot for posting the updated link 👍