问Go/Golang:如何从big.Float中提取最小有效数字？

EN

package main

import (
    "fmt"
    "math"
    "math/big"
)

func main() {
    // Replace with larger calculation.
    pi := big.NewFloat(math.Pi)

    const (
        // Pi: 3.1415926535897932...
        // Output: 5926535897
        digitOffset = 3
        digitLength = 10
    )

    // Move the desired digits to the right side of the decimal point.
    mult := pow(10, digitOffset)
    digits := new(big.Float).Mul(pi, mult)

    // Remove the integer component.
    digits.Sub(digits, trunc(digits))

    // Move the digits to the left of the decimal point, and truncate
    // to an integer representing the desired digits.
    // This avoids undesirable rounding if you simply print the N
    // digits after the decimal point.
    mult = pow(10, digitLength)
    digits.Mul(digits, mult)
    digits = trunc(digits)

    // Display the next 'digitLength' digits. Zero padded.
    fmt.Printf("%0*.0f\n", digitLength, digits)
}

// trunc returns the integer component.
func trunc(n *big.Float) *big.Float {
    intPart, accuracy := n.Int(nil)
    _ = accuracy
    return new(big.Float).SetInt(intPart)
}

// pow calculates n^idx.
func pow(n, idx int64) *big.Float {
    if idx < 0 {
        panic("invalid negative exponent")
    }
    result := new(big.Int).Exp(big.NewInt(n), big.NewInt(idx), nil)
    return new(big.Float).SetInt(result)
}