英文:
How does this Fibonacci code run with channels and go routines?
问题
有一个名为rosetta code的网站，其中包含各种语言的算法，因此您可以在学习新语言时进行学习和比较。
在这里，我看到Go语言的一个解决方案非常有趣，但我不完全理解它。
func fib(c chan int) {
a, b := 0, 1
for {
c <- a
a, b = b, a+b
}
}
func main() {
c := make(chan int)
go fib(c)
for i := 0; i < 10; i++ {
fmt.Println(<-c)
}
}
以下是我对此的一些疑问：
无限for循环如何知道何时停止？
c通道如何传达这一点？
func调用之间的逻辑顺序是什么？
感谢善良的陌生人的帮助。
英文:
There is this website called rosetta code that has algorithms in all languages so you can learn and compare when learning new languages.
Here I saw that one of the solutions for go lang is pretty interesting but I don't fully understand it.
func fib(c chan int) {
a, b := 0, 1
for {
c <- a
a, b = b, a+b
}
}
func main() {
c := make(chan int)
go fib(c)
for i := 0; i < 10; i++ {
fmt.Println(<-c)
}
}
Here are some of my doubts
How does the infinite for loop know when to stop?
How does the c channel communicate this?
What is the logical sequence between the func calls?
Thanks for the help kind strangers.
答案1
得分: 3
无限循环如何知道何时停止？
正如你所说：这是一个无限循环，只要程序在运行，它就不会停止。
c通道如何传达这一点？
c通道根本不会传达停止for循环的信息，循环不会停止。c的唯一目的是将计算站点（无限for循环）中的下一个数字传递到使用站点（打印循环）。
func调用之间的逻辑顺序是什么？
go fib(c)将fib作为goroutine启动。这是您的代码中唯一发生的函数调用（*）。一旦发生了go fib(c)，您就有两个并发的事情在运行：1.主函数将打印10次，2. fib(c)执行计算。
有趣的部分——main()和fib(c)之间的同步——发生在main执行<-c和（“在同一时刻”）fib执行c <- a时。当main和fib都达到这些行时，两者将“同时发生”：fib将写入/发送到c，main从c“同时”消费/接收。之后，main和fib函数都会独立继续执行。
一旦main完成，程序就会结束（这也会“停止”fib的无限循环）。
（*）对于吹毛求疵的人：除了对于理解此代码无关紧要的fmt.Printf和make调用。
英文:
> How does the infinite for loop know when to stop?
As you said: This is an infinite loop and doesn't stop at all (as long as the program is running).
> How does the c channel communicate this?
The channel c doesn't communicate stopping the for loop at all, the loop is not stopped. The sole purpose of c is to deliver the next number in the sequence from the calculation site (the infinite for loop) to the usage site (the print loop).
> What is the logical sequence between the func calls?
go fib(c) starts fib as a goroutine. This is the one and only function call (*) ever happening in your code. Once go fib(c) has happened you have to concurrent things running: 1. The main function which will print 10 times and 2. fib(c) which does the computation.
The interesting stuff -- the synchronization between main() and fib(c) -- happens when main executes <-c and ("in the same moment") fib executes c <- a. Both functions, main and fib work until they both reach those lines. Once both are "at that line", both will happen "at the same time": fib will write/send to c and main consumes/receives from c "simultaneous". Afterwards both functions main and fib continue independently.
Once main is done the program finishes (this also "stops" fib's infinite loop).
(*) for the nitpickers: besides the fmt.Printf and make call which are irrelevant for understanding of this code.
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