Go指南练习_错误

type ErrNegativeSqrt float64

func (e ErrNegativeSqrt) Error() string

package main

import (
    "fmt"
    "math"
)

type ErrNegativeSqrt float64  //创建一个新的类型

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)
    }
    return math.Sqrt(x), nil
}

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