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Problems with Go channels (2016)

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159 points mpweiher | 2 comments | 13 Apr 25 05:43 UTC | HN request time: 0s | source
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ricardobeat ◴[13 Apr 25 11:22 UTC] No.43671958[source]▶
Strange to go all this length without mentioning the approaches that solve the problem in that first example:

1. send a close message on the channel that stops the goroutine

2. use a Context instance - `ctx.Done()` returns a channel you can select on

Both are quite easy to grasp and implement.

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jtolds ◴[13 Apr 25 11:29 UTC] No.43671984[source]▶
Hi! No, I think you've misunderstood the assignment. The example posits that you have a "game" running, which should end when the last player leaves. While only using channels as a synchronization primitive (a la CSP), at what point do you decide the last player has left, and where and when do you call close on the channel?
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1. blablabla123 ◴[13 Apr 25 11:47 UTC] No.43672077[source]▶
I don't think channels should be used for everything. In some cases I think it's possible to end up with very lean code. But yes, if you have a stop channel for the other stop channel it probably means you should build your code around other mechanisms.

Since CSP is mentioned, how much would this apply to most applications anyway? If I write a small server program, I probably won't want to write it on paper first. With one possible exception I never heard of anyone writing programs based on CSP (calculations?)

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2. franticgecko3 ◴[13 Apr 25 18:35 UTC] No.43674842[source]▶
> Since CSP is mentioned, how much would this apply to most applications anyway? If I write a small server program, I probably won't want to write it on paper first. With one possible exception I never heard of anyone writing programs based on CSP (calculations?)

CSP is really in the realm of formal methods. No you wouldn't formulate your server program as CSP, but if you were writing software for a medical device, perhaps.

This is the FDR4 model checker for CSP, it's a functional programming language that implements CSP semantics and may be used to assert (by exhaustion, IIRC) the correctness of your CSP model.

https://cocotec.io/fdr/

I believe I'm in the minority of Go developers that have studied CSP, I fell into Go by accident and only took a CSP course at university because it was interesting, however I do give credit to studying CSP for my successes with Go.