gistfile1.scala

  /**
   * Splits the in collection into three collections, based on whether each element is assignable to X, Y or Z (in that order).
   */
  def filterByType3[X <: AnyRef : Manifest, Y <: AnyRef : Manifest, Z <: AnyRef : Manifest](in: Traversable[_]): (Seq[X], Seq[Y], Seq[Z]) = {
    val clax = manifest[X].runtimeClass
    val clay = manifest[Y].runtimeClass
    val claz = manifest[Z].runtimeClass

    def _filterByType3(in: Seq[_], xs: Vector[X], ys: Vector[Y], zs: Vector[Z]): (Seq[X], Seq[Y], Seq[Z]) = {
      in match {
        case Seq() => (xs, ys, zs)
        case Seq(a, as @ _*) =>
          if      (clax.isInstance(a)) _filterByType3(as, xs :+ a.asInstanceOf[X], ys,                      zs                     )
          else if (clay.isInstance(a)) _filterByType3(as, xs,                      ys :+ a.asInstanceOf[Y], zs                     )
          else if (claz.isInstance(a)) _filterByType3(as, xs,                      ys                     , zs :+ a.asInstanceOf[Z])
          else    _filterByType3(as, xs, ys, zs)
      }
    }

    _filterByType3(in.toSeq, Vector[X](), Vector[Y](), Vector[Z]())
  }