小编mar*_*ine的帖子

我在向朋友解释我期望Scala中的非尾递归函数比尾递归函数慢,所以我决定验证它.我用两种方式编写了一个很好的旧因子函数,并试图比较结果.这是代码:

def main(args: Array[String]): Unit = {
  val N = 2000 // not too much or else stackoverflows
  var spent1: Long = 0
  var spent2: Long = 0
  for ( i <- 1 to 100 ) { // repeat to average the results
    val t0 = System.nanoTime
    factorial(N)
    val t1 = System.nanoTime
    tailRecFact(N)
    val t2 = System.nanoTime
    spent1 += t1 - t0
    spent2 += t2 - t1
  }
  println(spent1/1000000f) // get milliseconds
  println(spent2/1000000f)
}

@tailrec
def tailRecFact(n: BigInt, s: BigInt …