在Go运算中处理浮点数精度?

问题描述

我对在Go中精确减去2个浮点数的方法感兴趣.

I'm interested in a way to accurately subtract 2 float's in Go.

我尝试使用math/big库，但无法获得准确的结果.

I've tried to use the math/big library but I can't get an accurate result.

我在Javascript中使用了 big.js 库来解决此问题. Go算法有类似的库/方法吗?

I've used the big.js library in Javascript which solves this problem. Is there a similar library/method for Go arithmetic?

    package main

    import (
        "fmt"
        "math/big"
    )

    func main() {
        const prec = 200
        a := new(big.Float).SetPrec(prec).SetFloat64(5000.0)
        b := new(big.Float).SetPrec(prec).SetFloat64(4000.30)
        result := new(big.Float).Sub(a, b)
        fmt.Println(result)
    }
    Result: 999.6999999999998181010596454143524169921875

https://play.golang.org/p/vomAr87Xln

推荐答案

导入数学/大"

func(* Float)字符串

func (x *Float) String() string

字符串格式x类似于x.Text('g'，10). (必须调用字符串 显然，Float.Format不支持％s动词.)

String formats x like x.Text('g', 10). (String must be called explicitly, Float.Format does not support %s verb.)

例如，使用字符串输入并四舍五入输出，

Use string input and round the output, for example,

package main

import (
    "fmt"
    "math/big"
)

func main() {
    const prec = 200
    a, _ := new(big.Float).SetPrec(prec).SetString("5000")
    b, _ := new(big.Float).SetPrec(prec).SetString("4000.30")
    result := new(big.Float).Sub(a, b)
    fmt.Println(result)
    fmt.Println(result.String())
}

输出:

999.6999999999999999999999999999999999999999999999999999999995
999.7

对于十进制，根据定义，二进制浮点数是一个近似值.例如，十进制数0.1不能精确表示，大约为1.10011001100110011001101 * (2**(-4)).

For decimal, by definition, binary floating-point numbers are an approximation. For example, the decimal number 0.1 cannot be represented exactly, it is approximately 1.10011001100110011001101 * (2**(-4)).

您已经习惯了这种事情，因为您知道重复小数，这是有理数的近似值:1 / 3 = .333...和3227 / 555 = 5.8144144144....

You are already used to this sort of thing since you know about repeating decimals, an approximation for rational numbers: 1 / 3 = .333... and 3227 / 555 = 5.8144144144....

请参见每个计算机科学家应该了解的有关浮动的知识点算法.

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