stupid-benchmark.scala

import scalaz.concurrent.Task

def benchmark[T](repeat: Int)(callback: => T): Unit = {
  var lastResult: Any = null
  var total = Duration.Zero

  for (i <- 0 until repeat) {
    val time = System.nanoTime()
    val result = callback
    val measured = (System.nanoTime() - time).nanos
    total += measured
    
    if (lastResult != result) {
      println(s"$i: Result: $result")
      lastResult = result
    }
    
    println(s"$i: Time: ${measured.toSeconds} seconds ($measured)")
  }
  
  println(s"Average: ${(total.toMillis.toDouble / 1000) / repeat} seconds")
}

def sum(n: Int, acc: Long = 0): Task[Long] = {
  if (n == 0) Task(acc) else
    Task(n).flatMap(x => sum(x-1, acc + x))
}

benchmark(repeat = 10)(sum(30000000).unsafePerformSync)