package main
import (
	"fmt"
	"github.com/spf13/cast"
	"math"
	"regexp"
	"strconv"
)

func main() {
	num1 := 5.335
	// 判斷幾位小數(shù)
	decimal, _ := CheckDecimal(cast.ToString(num1), "2")
	fmt.Println(decimal)

}

// CheckDecimal 判斷小數(shù)點后幾位小數(shù)點
// str 所要判斷的 小數(shù)字符串
// n 所要判斷的 位數(shù)
func CheckDecimal(str string, n string) (bool, error) {
	// 通過 regexp 的 正則比較
	// ([1-9]\d*) 1-9 的任意位數(shù)
	// (0) 或者第一位是 0
	// d{0,`+n+`} 0-n 位數(shù)
	return regexp.MatchString(`^(([1-9]\d*)|(0))(\.\d{0,`+n+`})?$`, str)
}

package main
import (
	"fmt"
	"github.com/spf13/cast"
	"math"
	"strconv"
)

func main() {
	num1 := 5.334
	fmt.Println(Float64Rand(num1,2))

}

//四舍五入
func Float64Rand(v float64, dig int) float64 {
	cDig := strconv.Itoa(dig)
	val := fmt.Sprintf("%0."+cDig+"f", v)
	return cast.ToFloat64(val)
}

package main
import (
	"fmt"
	"github.com/spf13/cast"
	"math"
	"strconv"
)

func main() {
	num1 := 5.334
	fmt.Println("num1:",num1)
	fmt.Println("res1:",FormatFloat(num1,2))
	num2 := 5.335
	fmt.Println("num2:",num2)
	fmt.Println("res2:",FormatFloat(num2,2))
	num3 := 5.336
	fmt.Println("num3:",num3)
	fmt.Println("res3:",FormatFloat(num3,2))
}

func FormatFloat(f float64, dig int) float64 {
	result := cast.ToFloat64(strconv.FormatFloat(f, 'f', dig+1, 64))
	pow := math.Pow(10, float64(dig))
	return math.Round(result*pow) / pow
}