package main

import (
	"errors"
	"fmt"
	"math"
)

type DivideError struct {
	Dividend int
	Divisor  int
}

func MySqrt(f float64) (float64, error) {
	if f < 0 {
		return 0, errors.New("math: square root of negative number")
	}
	return math.Sqrt(f), nil
}

func divide(a, b int) (int, error) {
	if b == 0 {
		return 0, errors.New("division by zero")
	}
	return a / b, nil
}

func (e *DivideError) Error() string {
	return fmt.Sprintf("cannot divide %d by %d", e.Dividend, e.Divisor)
}

func custom_divide(a, b int) (int, error) {
	if b == 0 {
		return 0, &DivideError{Dividend: a, Divisor: b}
	}
	return a / b, nil
}

func main() {
	// errors 接口
	err := errors.New("this is an error")
	fmt.Println(err)

	x := 16.0
	sqrt, err := MySqrt(x)
	if err != nil {
		fmt.Println("error:", err)
		return
	}
	fmt.Println("sqrt:", sqrt)

	// 显示返回错误
	result, err := divide(10, 0)
	if err != nil {
		fmt.Println("Error: ", err)
	} else {
		fmt.Println("Result: ", result)
	}

	// 自定义错误
	_, err = custom_divide(10, 0)
	if err != nil {
		fmt.Println(err)
	}
}