reduce vs fold

object reduce_vs_fold {
  println("Welcome to Eclipse Scala worksheet")       //> Welcome to Eclipse Scala worksheet

  def time[A](f: => A) = {
    val now = System.nanoTime
    val result = f
    val micros = (System.nanoTime - now) / 1000.0
    println("%12.4f micro seconds".format(micros))
    result
  }                                               //> time: [A](f: => A)A
  
  val a = time(Array.tabulate(100000)( x => util.Random.nextDouble))
                                                  //>   38750.0000 micro seconds
                                                  //| a  : Array[Double] = Array(0.6494449871627447, 0.3944213163608279, 0.3879756
                                                  //| 9727200987, 0.6299233458256341, 0.7337731563822277, 0.08374384043472749, 0.6
                                                  //| 187414133079476, 0.5920459843284207, 0.4207775384477208, 0.03771376791322289
                                                  //| 5, 0.13981062935305055, 0.3832567496603332, 0.39970286375198816, 0.344391495
                                                  //| 46946535, 0.32196739034561495, 0.6742217789803084, 0.6142433678961545, 0.494
                                                  //| 633963420701, 0.9556546875208423, 0.04043673927922464, 0.3146329810780646, 0
                                                  //| .14028952730663602, 0.27770713389856116, 0.14208941819772425, 0.828467725864
                                                  //| 924, 0.27285347541601246, 0.5258515850683053, 0.40600202438848443, 0.3746309
                                                  //| 8086650504, 0.27219975075843883, 0.24622631131168327, 0.501554144018367, 0.8
                                                  //| 35513875227377, 0.8111371432536196, 0.37311405905331607, 0.766744750468781, 
                                                  //| 0.6497923248904091, 0.04392105603605212, 0.050279817106685165, 0.01105965538
                                                  //| 8251044, 0.8913432487720093, 0.8554846952325842, 0.2697497450347266, 0.798
                                                  //| Output exceeds cutoff limit.
  
  val b = time(math.sqrt(a.map { x => math.pow(x, 2) }.reduce(_+_)))
                                                  //>   29987.0000 micro seconds
                                                  //| b  : Double = 182.6325768548345
  val c = time(math.sqrt(a.foldLeft(0.0) { (x, y) => x + math.pow(y, 2) }))
                                                  //>    7696.0000 micro seconds
                                                  //| c  : Double = 182.6325768548345
  
  println(a)                                      //> [D@21270107
}