doumor942473
doumor942473
2017-09-22 23:05
浏览 297
已采纳

在Go运算中处理浮点数精度?

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

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

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

图片转代码服务由CSDN问答提供 功能建议

我对准确地减去Go中2个浮点数的方法很感兴趣。 < p>我尝试使用 math / big 库,但无法获得准确的结果。

我使用了 big.js 库解决了此问题。

 包main 
 
 import(
“ fmt” 
“ math / big” 
)
有类似的库/方法吗?  
 func main(){
 const prec = 200 
a:= new(big.Float).SetPrec(prec).SetFloat64(5000.0)
b:= new(big.Float).SetPrec(prec).SetFloat64  (4000.30)
结果:= new(big.Float).Sub(a,b)
 fmt.Println(result)
} 
结果:999.6999999999998198181010596454143524169921875 
   
 \  n 

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

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2条回答 默认 最新

  • doushoubu5360
    doushoubu5360 2017-09-22 23:08
    已采纳

    Package big

    import "math/big"

    func (*Float) String

    func (x *Float) String() string
    

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

    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())
    }
    

    Output:

    999.6999999999999999999999999999999999999999999999999999999995
    999.7
    

    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)).

    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....

    See What Every Computer Scientist Should Know About Floating-Point Arithmetic.

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  • duanou1904
    duanou1904 2017-09-24 08:20

    Maybe try github.com/shopspring/decimal.

    It calls itself a package for "arbitrary-precision fixed-point decimal numbers in go".

    NOTE: can "only" represent numbers with a maximum of 2^31 digits after the decimal point.

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