英文:
How to replicate do while in go?
问题
我想要一段代码，直到用户明确想要退出函数时才执行。例如：当用户运行程序时，他将看到2个选项：
- 再次运行
- 退出
这可以使用switch case结构来实现。如果用户按下1，与1相关联的一组函数将执行，如果用户按下2，程序将退出。我应该如何在Go语言中实现这种情况？在Java中，我相信可以使用do while结构来实现，但Go语言不支持do while循环。以下是我尝试过的代码，但它进入了一个无限循环：
func sample() {var i = 1for i > 0 {fmt.Println("Press 1 to run")fmt.Println("Press 2 to exit")var input stringinpt, _ := fmt.Scanln(&input)switch inpt {case 1:fmt.Println("hi")case 2:os.Exit(2)default:fmt.Println("def")}}}
无论输入是什么，程序都只打印"hi"。请问有人能纠正我在这里做错了什么吗？
谢谢。
英文:
I want a set of code to be executed until user explicitly wants to exit the function. For eg: when a user runs the program, he will see 2 options:
- Run again
- Exit
this will be achieved using switch case structure. Here if user presses 1, set of functions associated with 1 will execute and if user presses 2, the program will exit. How should i achieve this scenario in golang ? In java, i believe this could be done using do while structure but go doesn't support do while loop. Following is my code which i tried but this goes in a infinite loop:
func sample() {var i = 1for i > 0 {fmt.Println("Press 1 to run")fmt.Println("Press 2 to exit")var input stringinpt, _ := fmt.Scanln(&input)switch inpt {case 1:fmt.Println("hi")case 2:os.Exit(2)default:fmt.Println("def")}}}
The program irrespective of the input, prints only "hi". Could someone please correct me what wrong i am doing here ?
Thanks.
答案1
得分: 80
一个 do..while 循环可以在 Go 中通过使用一个以 true 为初始值的 bool 循环变量来更直接地模拟。
for ok := true; ok; ok = EXPR { }
几乎等同于
do { } while(EXPR)
所以在你的情况下：
var input intfor ok := true; ok; ok = (input != 2) {n, err := fmt.Scanln(&input)if n < 1 || err != nil {fmt.Println("invalid input")break}switch input {case 1:fmt.Println("hi")case 2:// 什么都不做（我们想要退出循环）// 在一个真实的程序中，这可能是清理操作default:fmt.Println("def")}}
编辑：Playground（使用虚拟的 Stdin）
尽管如此，在这种情况下，直接在循环中明确调用（带标签的）break、return 或 os.Exit 可能更清晰明了。
英文:
A do..while can more directly be emulated in Go with a for loop using a bool loop variable seeded with true.
for ok := true; ok; ok = EXPR { }
is more or less directly equivalent to
do { } while(EXPR)
So in your case:
var input intfor ok := true; ok; ok = (input != 2) {n, err := fmt.Scanln(&input)if n < 1 || err != nil {fmt.Println("invalid input")break}switch input {case 1:fmt.Println("hi")case 2:// Do nothing (we want to exit the loop)// In a real program this could be cleanupdefault:fmt.Println("def")}}
Edit: Playground (with a dummied-out Stdin)
Though, admittedly, in this case it's probably overall clearer to just explicitly call (labelled) break, return, or os.Exit in the loop.
答案2
得分: 14
当这个问题被提出时，这个答案对于这个特定的场景来说是更好的（我并不知道这将成为在谷歌搜索“do while loop golang”时的第一结果）。如果要通用地回答这个问题，请参考@LinearZoetrope的答案。
将你的函数包装在一个for循环中：
package mainimport ("fmt""os")func main() {fmt.Println("按1运行")fmt.Println("按2退出")for {sample()}}func sample() {var input intn, err := fmt.Scanln(&input)if n < 1 || err != nil {fmt.Println("无效的输入")return}switch input {case 1:fmt.Println("你好")case 2:os.Exit(2)default:fmt.Println("默认")}}
在其他类似C语言的语言中，没有任何声明的for循环等同于while循环。请查看Effective Go文档中关于for循环的内容。
英文:
When this question was asked this was a better answer for this specific scenario (little did I know this would be the #1 result when searching Google for "do while loop golang"). For answering this question generically please see @LinearZoetrope's answer below.
Wrap your function in a for loop:
package mainimport ("fmt""os")func main() {fmt.Println("Press 1 to run")fmt.Println("Press 2 to exit")for {sample()}}func sample() {var input intn, err := fmt.Scanln(&input)if n < 1 || err != nil {fmt.Println("invalid input")return}switch input {case 1:fmt.Println("hi")case 2:os.Exit(2)default:fmt.Println("def")}}
A for loop without any declarations is equivalent to a while loop in other C-like languages. Check out the Effective Go documentation which covers the for loop.
答案3
得分: 14
在Go语言中，do...while循环可以使用以下方式实现：
func main() {var value intfor {value++fmt.Println(value)if value%6 != 0 {break}}}
这段代码会不断地增加value的值，并打印出来。当value不能被6整除时，循环会被终止。
英文:
The do...while in go can be this:
func main() {var value intfor {value++fmt.Println(value)if value%6 != 0 {break}}}
答案4
得分: 13
在Go语言中，一个while循环可以这么简单地实现：
package mainimport "fmt"func main() {for {var number float64fmt.Print("请输入一个大于等于10的整数：")fmt.Scanf("%f", &number)if number >= 10 {break}fmt.Println("抱歉，数字小于10，请重新输入！")}}
这段代码实现了一个无限循环，要求用户输入一个大于等于10的整数，如果输入的数字小于10，则会提示用户重新输入。直到用户输入的数字大于等于10时，循环才会结束。
英文:
a while loop in Go can be as easy as this:
package mainimport `fmt`func main() {for {var number float64fmt.Print(`insert an Integer eq or gr than 10!!!`)fmt.Scanf(`%f`, &number)if number >= 10 { break }fmt.Println(`sorry the number is lower than 10....type again!!!`)}
答案5
得分: 4
考虑使用"for-break"替代"do-while"。
foo.go
package mainimport ("fmt")func main() {i := 0for {i++if i > 10 {break}fmt.Printf("%v ", i)}fmt.Println()}
shell
$ go run foo.go1 2 3 4 5 6 7 8 9 10
英文:
Conside to use "for-break" as "do-while".
foo.go
package mainimport ("fmt")func main() {i := 0for {i++if i > 10 {break}fmt.Printf("%v ", i)}fmt.Println()}
shell
$ go run foo.go1 2 3 4 5 6 7 8 9 10
答案6
得分: 2
也许不是你要找的，但如果你想要做类似的事情，你可以这样在Go语言中实现：
package mainimport "fmt"func main() {i := 0fmt.Println(i)for {if i < 10 {fmt.Println("incrementing i now")i++} else {break}}fmt.Println("done")}
这段代码会输出：
0incrementing i nowincrementing i nowincrementing i nowincrementing i nowincrementing i nowincrementing i nowincrementing i nowincrementing i nowincrementing i nowincrementing i nowdone
希望对你有帮助！
英文:
Maybe not what you're looking for, but if you're trying to do something like this:
int i = 0;while (i < 10) {cout << "incrementing i now" << endl;i++}cout << "done"
You'll have to do something like this in go:
var i = 0fmt.Println(i)for {if i < 10 {fmt.Println("incrementing i now")i++} else {break}}fmt.Println("done")
答案7
得分: 1
sum := 1
for sum < 1000 {
sum += sum
}
解释：
基本的for循环由三个部分组成，用分号分隔：
-
init语句：在第一次迭代之前执行。
-
condition表达式：在每次迭代之前进行评估。
-
post语句：在每次迭代结束时执行。
init语句和post语句是可选的。
因此，你可以只放入condition表达式。
// 当(CONDITION = true)时执行以下代码....
// 在Go语言中：
for CONDITION = true {
// 要执行的代码
}
英文:
sum := 1for sum < 1000 {sum += sum}
Explanation :
The basic for loop has three components separated by semicolons:
-the init statement: executed before the first iteration.
-the condition expression: evaluated before every iteration
-the post statement: executed at the end of every iteration
The init and post statements are optional.
So you can just put in the condition expression.
// While (CONDITION = true){//code to execute ....}//In go :for CONDITION = true {//code to execute}
答案8
得分: 0
这是其中一种最简洁的方式：
num := 10for num > 0 {// 在这里执行操作num--}
英文:
This is one of the cleanest ways:
num := 10for num > 0 {// do stuff herenum--}
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