learn go recursive

package main

// 参考文章：
//     https://github.com/Unknwon/the-way-to-go_ZH_CN/blob/master/eBook/06.6.md

import (
    "fmt"
)

func main () {
     fmt.Printf("%d is even: is %t\n", , even()) // 16 is even is true
    fmt.Printf("%d is odd: is %t\n", , odd())
    // 17 is odd: is true
    fmt.Printf("%d is odd: is %t\n", , odd())
    // 18 is odd: is false
}

func even( nr int) bool {
    if nr ==  {
        return true
    }
    return odd(RevSign(nr) - )
}

func odd(nr int) bool {
    if nr ==  {
        return false
    }
    return even(RevSign(nr) - )
}

func RevSign(nr int) int {
    if nr <  {
        return -nr
    }
    return nr
}