golang初学之接口实现

package main

import (
	"fmt"
)

type ErrNegativeSqrt float64
// 实现Error接口，ErrNegativeSqrt 可以作为一个error来用
func (e ErrNegativeSqrt) Error() string {
	return fmt.Sprintf("cannot Sqrt negative number: %v", float64(e))
}

func Sqrt(x float64) (float64, error) {
	if x < 0 {
		return 0, ErrNegativeSqrt(x)
	}
	z := x/2
	var t float64
	for  {
		t = z
		z = z - (z*z - x)/(2*x)
		if t - z > -0.001 && t - z < 0.001 {
			break
		}
	}
	return z, nil
}

func main() {
	fmt.Println(Sqrt(2))
	fmt.Println(Sqrt(-2))
}