prime factorization in scala

prime-factors.scala

  // borrowed from http://louisbotterill.blogspot.com/2009/03/prime-factorization-comparison-between.html
  def factors(n:Int):List[Int] = {
    def divides(d:Int, n:Int) = (n % d) == 0
    def ld(n:Int):Int =  ldf(2, n)
    def ldf(k:Int, n:Int):Int = {
      if (divides(k, n)) k
      else if ((k*k) > n) n
      else ldf((k+1), n)
    }
    n match {
      case 1 => Nil
      case _ => val p = ld(n); p :: factors(n / p)
    }
  }