package main

import "fmt"

//func main() {
//	fmt.Print("123")
//	appendTest()
//	x := []int{1, 2, 3}
//	appendIndex(x, 4)
//}

func appendTest() {
	var runes []rune
	for _, r := range "Hello world" {
		runes = append(runes, r)
	}
	fmt.Printf("%q\n", runes)
}

func appendIndex(x []int, y int) []int {
	var z []int
	zlen := len(x) + 1 //因为要添加一个int
	fmt.Println(len(x))
	fmt.Println(cap(x))
	fmt.Println(zlen)

	if zlen <= cap(x) {
		z = x[:zlen]
	} else {
		zcap := zlen
		if zcap < 2*len(x) {
			zcap = 2 * len(x)
		}
		fmt.Printf("2*len is cap=%d\n", zcap)
		fmt.Printf("2*len is zlen=%d\n", zlen)
		z = make([]int, zlen, zcap)
		copy(z, x) //将 x []int 中原始的数据复制到 z []int中去
	}
	z[len(x)] = y //将新append的元素添加到位置为len(x)处
	return z      //返回 []int

}