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Comment by Joker_vD | Hacker News Reader

Wait, how do you run two coroutines in parallel? Like, how do I write zip() or something like it?

    a() -> Int() | Void
    b() -> Int() | Void

    for(a()) {
        | na -> for(b()) {
            | nb ->
                print(na + nb)
                // now what? From here, I want to continue to a(), not b()

I don't believe there is much use for coroutines without support for their interleaved execution.

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Generators are a thing in multiple languages that are essentially this (javascript, C# to name a couple). It’s nice for creating lazily iterators ergonomically

Such a language would certainly have some way to take a single value from a coroutine. Probably just an omission by the author.

Yes, I know it's an omission by the author but since the interleaving is IMHO the sine qua non for coroutines it's a glaring omission. Without it, the whole proposal looks like a large heap of machinery and complicated syntax that still only supports sequential execution which traditional languages support well enough already, thanks.

Wait, like, there isn't any data being passed to those functions so they have like no data dependencies and can be like run in parallel and buffered.

Interleaving is so synchronous.

You have to liberate yourself from tick-tock synchrony.

There are 'a' and 'b' processes, they generate messages. You cannot predict how those will arrive. If you want them strictly alternating, you can tag each of the messages with the source, and block until you get the next other one you expect. Or you can just receive them all and make sense of them on their own terms.

> You have to liberate yourself from tick-tock synchrony.

Thank you for telling me which kinds of program I am not allowed to write any more in the bright new future of the programming.

As for the rest of your comment, I am aware of CSP and its derivatives, thanks. The question was about the language proposed in TFA that seems to be lacking the choice/select primitive.

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