Scala unzip

gistfile1.scala

/* unzip decomposes a list of pairs into a pair of lists.
   * The recursive case illustrates pattern-matching the result of the
   * recursive call in order to apply an operation to the elements.
   */
def unzip [X,Y] (ps:List[(X,Y)]) : (List[X], List[Y]) = ps match {
  case Nil      => (Nil, Nil)
  case (x, y) :: qs => {
    val (xs, ys) = unzip (qs)
    (x :: xs, y :: ys)
  }
}