fold_bench.scala

object Main extends App {
  val list = (1 to 10000).toVector

  val start = System.currentTimeMillis()
  val a = mapA(list)(_ * 2)
  println(s"a elap = ${System.currentTimeMillis() - start}ms")

  val start2 = System.currentTimeMillis()
  val b = mapB(list)(_ * 2)
  println(s"b elap = ${System.currentTimeMillis() - start2}ms")

  val start3 = System.currentTimeMillis()
  val c = mapC(list)(_ * 2)
  println(s"c elap = ${System.currentTimeMillis() - start3}ms")

  def mapA[A, B](list: Seq[A])(f: A => B): Seq[B] = list.foldLeft(Seq.empty[B])((acc, x) => acc :+ f(x))
  def mapB[A, B](list: Seq[A])(f: A => B): Seq[B] = list.reverse.foldLeft(Seq.empty[B])((acc, x) => f(x) +: acc)
  def mapC[A, B](list: Vector[A])(f: A => B): Vector[B] = list.foldLeft(Vector.empty[B])((acc, x) => acc :+ f(x))
}


/*

[info] Running Main
a elap = 1554ms
b elap = 30ms
c elap = 16ms

*/