the wave in scala

// http://stackoverflow.com/questions/1376077/code-golf-the-wave

object Wave {
  def main(args: Array[String]) {
    val s = if (!args.isEmpty) args(0) else "31415926535897932384626433832795028841971693993751058209749445923078164062862"
    val (ls, _) = ((Map() + 0 -> s.substring(0, 1), 0) /: s.toList.zipWithIndex.tail) {
      case ((ls, y), (c, i)) =>
        val d = y + (c compare s(i - 1))
        ((ls + d -> (ls.getOrElse(d, "") match { case z => z + (" " * (i - z.length)) + c })), d)
    }

    println(ls.keys.toList sort { _ > _ } map ls mkString "\n")
  }
}