Example of sorting list of lists

test.scala

import annotation.tailrec
import scala.math.Ordering
import scala.util.Random

class ListOrdering extends Ordering[List[Int]] {
  @tailrec final def compare(as:List[Int], bs:List[Int]) = (as, bs) match {
    case (Nil, Nil) => 0
    case (Nil, _) => -1
    case (_, Nil) => 1
    case (a::as, b::bs) if a < b => -1
    case (a::as, b::bs) if b < a => 1
    case (a::as, b::bs) => compare(as, bs)
  }
}

object Test {

  def main(args:Array[String]) {
    val m = 10000 // # of sublists
    val n = 50 // # of items per sublist
    val o = 1000 // range of int values in each sublist

    def makeInt() = scala.math.abs(Random.nextInt % o).toInt
    def makeList() = (0 until n).toList.map(i => makeInt)
    def makeLists() = (0 until m).toList.map(i => makeList)

    val data = makeLists()
    implicit val listOrder = new ListOrdering()

    val t0 = System.currentTimeMillis()
    val data2 = data.sorted
    val t = System.currentTimeMillis() - t0

    println("sorted %d lists of length %d in %d ms" format (m, n, t))
  }
}