compute all permutations of a string

permutations.scala

object per extends App{
  def permutations(str: String):List[String] = {
    if(str.size == 0)
      List("")
    else{
      val res = {
        for{c <- str
            per <- permutations(str.replaceFirst(c.toString, ""))
        }yield c + per
      }
▫▫
      res.toList
    }
  }

  val res = permutations("abc")
  res.foreach(println)
}