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Comment by drudru11 | Hacker News Reader

Which parts are the coroutines?

Multiple methods in that snippet use something like:

    while(true) {
        Animate(image);
        wait 200;
    }

implies there are multiple synchronous execution stacks. It's not threading, as the synchronization points are explicit.

>synchronization points are explicit

Hmmm, I'd have just called it cooperative threading/multitasking then. Or do you think that would be wrong?

Coroutines and cooperative threading/multitasking are indeed threading. I assume they meant to say that it was neither preemptive nor parallel, which makes it somewhat limited. Some people think a system has to be one or both of those to be called threading.

For me, and for a vast majority of people I'd say, the word "threading" in common parlance implies pre-emptive scheduling with implicit synchronization points.

It wouldn't. That's literally what coroutines are. In-process, lightweight, cooperative multitasking, built in as a language feature (or at least close enough to it).

It is not. Coroutines are a much more fundamental feature. They can be used to implement cooperative multitasking, and since that is such a common use case, they have gotten confused with the concept of cooperative multitasking.

Actual coroutines are a lot more flexible and interesting than just cooperative multitasking, though.

Erm, I'm pretty sure I can implement coroutines using cooperative multitasking. Also, the other way around. So I'd say they're equivalent in that sense.

Cooperative multitasking usually involves a scheduler. Coroutines are called explicitly, which you can't do through a scheduler.

Now you're really just making claims about implementation details. That doesn't make one concept more "fundamental" or "flexible" than the other, while "interesting" is just a subjective judgement.

I'm not. The scheduler decides what code to execute next, the caller does not. With coroutines, the caller explicitly decides what code to execute next. That's a fundamental difference.

Explicitly selecting what code to execute next can be trivially achieved in a cooperative multitasking system. Naturally, the details work out differently. That's because both concepts are equivalent, just not the same.

Sure, you could implement some kind of anti-scheduler, but that is just plain silly, and really doesn't affect the point at all. You can do anything in any Turing-complete language, but that doesn't mean that Brainfuck is equivalent to Prolog in any way that is actually useful or interesting.

That's like saying that implementing a scheduler using coroutines is silly. Yet people do it all the time. * You may keep moving the goal posts all you want, your original claims were wrong and they stay wrong.

Can't you just say something like "I like coroutines more, they are so minimalist and elegant, and yet they are equivalent in power to cooperative multitasking!". I'd actually subscribe to that notion. But not your overblown claims of objective superiority.

* One has to wonder why so many people crave a scheduler, when they already have coroutines? Maybe because having a scheduler makes certain things easier than naked coroutines?

It's not, that is a perfectly logical thing to do: Use a more generic primitive to implement more specific functionality.

It's not about liking one thing or another more. It's that coroutines are coroutines, and cooperative multitasking is cooperative multitasking. The two are often confused, and all I am saying is that that is incorrect.

Cooperative multitasking can easily be implemented with coroutines, but doesn't have to be. You could implement coroutines with cooperative multitasking but doing so is highly silly and a massive hack.

>The two are often confused, and all I am saying is that that is incorrect.

And both are equally capable is all I'm saying.

Well, I suppose we've come close enough then to move on.

With coroutines, your program logic itself is the scheduler.

Thus why coroutines are more fundamental and powerful.

cooperative threading is just coroutines plus a scheduler.

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