scala求列表元素平均值

import scala.language.implicitConversions

object 求列表元素平均值 {

  class RichList(list: List[Int]) {
    def avg(): Option[Int] = {
      if (list.isEmpty)
        None
      else
        Some(list.sum / list.size)
    }
  }

  def main(args: Array[String]): Unit = {

    implicit def list2RichList(list: List[Int]): RichList = new RichList(list)

    val list = List(1, 2, 3, 4, 5)
    println(list.avg())

  }

}