@@ -72,8 +72,37 @@ class Random(val self: java.util.Random) { } /** The object <code>Random</code> offers a default implementation - * of scala.util.Random. + * of scala.util.Random and random-related convenience methods. * * @since 2.8 */ object Random extends Random +{ + import collection.Sequence + + /** Returns a new sequence in random order. + * @param seq the sequence to shuffle + * @return the shuffled sequence + */ + def shuffle[T](seq: Sequence[T]): Sequence[T] = { + // It would be better if this preserved the shape of its container, but I have + // again been defeated by the lack of higher-kinded type inference. I can + // only make it work that way if it's called like + // shuffle[Int,List](List.range(0,100)) + // which nicely defeats the "convenience" portion of "convenience method". + val buf: Array[T] = seq.toArray + + def swap(i1: Int, i2: Int) { + val tmp = buf(i1) + buf(i1) = buf(i2) + buf(i2) = tmp + } + + for (n <- buf.length to 2 by -1) { + val k = nextInt(n) + swap(n - 1, k) + } + + buf.toSeq + } +} src/library/scala/util/Random.scala c416256772c6ced49b9ef954d20e2449e5de6222 extempore extempore@5e8d7ff9-d8ef-0310-90f0-a4852d11357a http://github.com/jorgeortiz85/scala/commit/4133571d758fd4ff2511b2bafa031eba625f87c3 4133571d758fd4ff2511b2bafa031eba625f87c3 2009-05-28T08:51:07-07:00 2009-05-28T08:51:07-07:00 Added a sequence shuffling method to scala.util.Random. git-svn-id: http://lampsvn.epfl.ch/svn-repos/scala/scala/trunk@17884 5e8d7ff9-d8ef-0310-90f0-a4852d11357a b7e2bf06a12a61af7069244eb5b9c4f36616d738 extempore extempore@5e8d7ff9-d8ef-0310-90f0-a4852d11357a