float 精度问题

package main

import "fmt"

func main() {
	var n float64 = 0
	for i := 0; i < 1000; i++ {
		n += .01
	}
	fmt.Println(n)
}

结果//9.999999999999831

1/3 问题

import "fmt"
import "math/big"

func main() {
	z, _ := new(big.Rat).SetString("1")
	three, _ := new(big.Rat).SetString("3")
	x := new(big.Rat).Quo(z, three)
	y := new(big.Rat).Quo(z, three)

	z = z.Sub(z, x)
	z = z.Sub(z, y)
	
	s := new(big.Rat).Add(x, y)
	s.Add(s, z)

	fmt.Println(x.FloatString(3), "+") // 0.333
	fmt.Println(y.FloatString(3), "+") // 0.333
	fmt.Println(z.FloatString(3))      // 0.333
	fmt.Println("=", s.FloatString(3)) // where did the other 0.001 go?
}