package main// 参考文章：//     https://github.com/Unknwon/the-way-to-go_ZH_CN/blob/master/eBook/06.6.mdimport (    "fmt")func main () {     fmt.Printf("%d is even: is %t\n", 16, even(16)) // 16 is even is true    fmt.Printf("%d is odd: is %t\n", 17, odd(17))    // 17 is odd: is true    fmt.Printf("%d is odd: is %t\n", 18, odd(18))    // 18 is odd: is false}func even( nr int) bool {    if nr == 0 {        return true    }    return odd(RevSign(nr) - 1)}func odd(nr int) bool {    if nr == 0 {        return false    }    return even(RevSign(nr) - 1)}func RevSign(nr int) int {    if nr < 0 {        return -nr    }    return nr}