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The scope of break and continue in golang select is strange #43889

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guonaihong opened this issue Jan 25, 2021 · 4 comments
Closed

The scope of break and continue in golang select is strange #43889

guonaihong opened this issue Jan 25, 2021 · 4 comments
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@guonaihong
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code 1

// output: 0 1 2 4 
package main

import (
	"fmt"
)

func main() {

	data := make(chan int)
	go func() {
		for i := 0; i < 5; i++ {
			data <- i
		}
		close(data)
	}()

	for {
		v := 0
		ok := true
		select {
		case v, ok = <-data:
			if v == 3 {
				continue
			}

			if !ok {
				return
			}

		}
		fmt.Printf("v :%d\n", v)
	}
}

code 2

replace continue with break

//output: 0 1 2 3 4 
package main

import (
	"fmt"
)

func main() {

	data := make(chan int)
	go func() {
		for i := 0; i < 5; i++ {
			data <- i
		}
		close(data)
	}()

	for {
		v := 0
		ok := true
		select {
		case v, ok = <-data:
			if v == 3 {
				break
			}

			if !ok {
				return
			}

		}
		fmt.Printf("%d ", v)
	}
}

why

break affects select, continue affects for. This is easy to confuse people, why was it designed like this in the first place
@mdempsky
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Unlike many projects, the Go project does not use GitHub Issues for general discussion or asking questions. GitHub Issues are used for tracking bugs and proposals only.

For asking questions, see:

If we closed your issue as a question with a link to this wiki, we apologize. Please ask the question on one of the above forums.

@guonaihong
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My question is about semantics. It is difficult to answer if it is not the person who made the decision.

@guonaihong
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What I am curious about is why it is designed like this.

@mdempsky
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Please ask your question on one of the above forums.

@golang golang locked and limited conversation to collaborators Jan 25, 2022
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@mdempsky @guonaihong @gopherbot