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Golang浮点数比较和运算会出现误差。
浮点数储存至内存中时,2的-1、-2……-n次方不能精确的表示小数部分,所以再把这个数从地址中取出来进行计算就出现了偏差。
package main
import (
"errors"
"fmt"
"github.com/shopspring/decimal"
)
func FloatCompare(f1, f2 interface{}) (n int, err error) {
var f1Dec, f2Dec decimal.Decimal
switch f1.(type) {
case float64:
f1Dec = decimal.NewFromFloat(f1.(float64))
switch f2.(type) {
case float64:
f2Dec = decimal.NewFromFloat(f2.(float64))
case string:
f2Dec, err = decimal.NewFromString(f2.(string))
if err != nil {
return 2, err
}
default:
return 2, errors.New("FloatCompare() expecting to receive float64 or string")
}
case string:
f1Dec, err = decimal.NewFromString(f1.(string))
if err != nil {
return 2, err
}
switch f2.(type) {
case float64:
f2Dec = decimal.NewFromFloat(f2.(float64))
case string:
f2Dec, err = decimal.NewFromString(f2.(string))
if err != nil {
return 2, err
}
default:
return 2, errors.New("FloatCompare() expecting to receive float64 or string")
}
default:
return 2, errors.New("FloatCompare() expecting to receive float64 or string")
}
return f1Dec.Cmp(f2Dec), nil
}
func main() {
a:=4.0
b:="4"
fmt.Println(FloatCompare(a,b))
}
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