Scala comb search

mnem encode.scala

import scala.io.Source

object mnem {
  val in = Source.fromURL("http://lamp.epfl.ch/files/content/sites/lamp/files/teaching/progfun/linuxwords.txt")

  val words = in.getLines.toList filter (word => word forall (c => c.isLetter))

  val mnem = Map(
  	'2' -> "ABC", '3' -> "DEF", 4 -> "GHI", '5' -> "JKL",
  	'6' -> "MNO", '7' -> "PQRS", '8' -> "TUV", 9 -> "WXYZ")

  val charCode: Map[Char, Char] =
    for {
     (digit:Char, str) <- mnem
     ltr <- str
    } yield ltr -> digit
    
	def wordCode(word: String) =
		word.toUpperCase map charCode

	val wordsForNum: Map[String, Seq[String]] =
		words groupBy wordCode withDefaultValue Seq()
		
  def encode(number: String): Set[List[String]] =
 		if (number.isEmpty) Set(List())
 		else {
 			for {
 				split <- 1 to number.length
 				word <- wordsForNum(number take split)
 				rest <- encode(number drop split)
 			} yield word :: rest
 		}.toSet
 		
 	def translate(number: String): Set[String] =
 		encode(number) map (_ mkString " ")
 		
 	translate("7225247386")
}

nqueens.scala

object nqueens {
  def queens(n: Int): Set[List[Int]] = {
    def placeQueens(k: Int): Set[List[Int]] = {
    	if (k == 0) Set(List())
    	else
    		for {
    			queens <- placeQueens(k - 1)
    			col <- 0 until n
    			if isSafe(col, queens)
    		} yield col :: queens
    }
    placeQueens(n)
  } 
 
  def isSafe(col: Int, queens: List[Int]): Boolean = {
  	val row = queens.length
  	val queensWithRow = (row - 1 to 0 by -1) zip queens
  	queensWithRow forall {
  		case (r,c) => col != c && math.abs(col - c) != row - r
    }
  }

  queens(4)                                       //> res0: Set[List[Int]] = Set(List(1, 3, 0, 2), List(2, 0, 3, 1))
    			
}