dongtuoao7987 2017-01-24 22:23
浏览 108
已采纳

Golang中的奇怪Pow实现

I just came across the Pow implementation in golang:

func Pow(x, y float64) float64 {
    // ...
    case x == 0:
        switch {
        case y < 0:
            if isOddInt(y) {
                return Copysign(Inf(1), x)
            }
            return Inf(1)
        case y > 0:
            if isOddInt(y) {
                return x
            }
            return 0
        }
    //...
}

Isn't the case y > 0 part over complicated? I would just return 0. Or did I miss something?

  • 写回答

2条回答 默认 最新

  • doulang9953 2017-01-24 23:02
    关注

    there are two types of zero's, +0 and -0. return value of Pow(-0,1) should be -0 not +0

    to create -0 in golang, use math.Copysign.

    x := math.Copysign(0, -1)
    if x == 0 {
        fmt.Println("x is zero")
    }
    fmt.Println("x ** 3 is", math.Pow(x, 3))
    

    the output of above code is

    x is zero
    x ** 3 is -0
    

    you can check it in Go Playground

    why we have to distinguish +0 and -0, see: https://softwareengineering.stackexchange.com/questions/280648/why-is-negative-zero-important

    本回答被题主选为最佳回答 , 对您是否有帮助呢?
    评论
查看更多回答(1条)

报告相同问题?

悬赏问题

  • ¥15 微信公众号如何开发网页
  • ¥15 h3.6m 人类行为预测论文复现
  • ¥50 wordpress项目注册报失败刷新后其实是成功状态,请求排查原因
  • ¥20 linxu服务器僵尸进程不释放,代码如何修改?
  • ¥15 pycharm激活不成功
  • ¥40 如果update 一个列名为参数的value
  • ¥15 基于51单片机的水位检测系统设计中LCD1602一直不显示
  • ¥15 OCS2安装出现问题,请大家给点意见
  • ¥15 ros小车启动launch文件报错
  • ¥15 vs2015到期想登陆但是登陆不上