[kragen]

cooperative multitasking, as i use the term, keeps you from having to transform your code. it maintains a separate stack per task, just like preemptive multitasking. so async/await isn't cooperative multitasking, though it can achieve similar goals

possibly you are using the terms in subtly different ways so it appears that we disagree when we do not

[nottorp]

Cooperative multitasking is "The illusion of simultaneously executing code paths by having said code paths pass control to each other fast enough."

If the OS forcefully switches control it's preemptive.

[kragen]

that definition is different from the definition i'm using; it covers both what i'm calling 'cooperative multitasking' and things like async/await, the npm event handler model, and python/clu iterators

in the mac os 8 documentation, explaining how mac os 8 only has 'cooperative multitasking', the term is defined in the way i'm using it (https://developer.apple.com/library/archive/documentation/Ca...):

> In programming, a task is simply an independent execution path. On a computer, the system software can handle multiple tasks, which may be applications or even smaller units of execution. For example, the system may execute multiple applications, and each application may have independently executing tasks within it. Each such task has its own stack and register set.

> Multitasking may be either cooperative or preemptive. Cooperative multitasking requires that each task voluntarily give up control so that other tasks can execute. (...)

> The Mac OS 8 operating system implements cooperative multitasking between applications. The Process Manager can keep track of the actions of several applications. However, each application must voluntarily yield its processor time in order for another application to gain it. An application does so by calling WaitNextEvent, which cedes control of the processor until an event occurs that requires the application’s attention.

that is, this requirement that each task have its own stack is not just something i made up; it's been part of common usage for decades, at least in some communities. the particular relevant distinction here is that, because each task has its own stack (or equivalent in something like scheme), multitasking doesn't require restructuring your code, because calling a normal function can yield the cpu. in the specific case of macos this was necessary so that switcher/multifinder/process-manager could multitask mac apps written for previous versions of macos that didn't have multitasking

what term would you propose for what i'm calling 'cooperative multitasking', like forth and mac os 8 and windows 3.1 (https://softwareengineering.stackexchange.com/questions/3507... https://retrocomputing.stackexchange.com/questions/791/how-d...)? this terminology is not absolutely standardized, and i'd be happy to use different terminology in order to be able to communicate productively

also could you please answer my request for clarification in https://news.ycombinator.com/item?id=38861074

[nottorp]

> it covers both what i'm calling 'cooperative multitasking' and things like async/await, the npm event handler model, and python/clu iterators

Those are implementation details. What's actually happening in all cases is my definition.

> also could you please answer my request for clarification in

Yes, your examples or the 5 million other implementations of event loops. You forgot to add gtk's for example :)

> in the mac os 8 documentation

... and I see no mention of stacks on Wikipedia:

https://en.wikipedia.org/wiki/Cooperative_multitasking

Which lumps in both the explicit event loop style and the syntactic sugar that got added later.

We could throw definitions around till kingdom come like this. And it's not the exact definition that's my problem.

[kragen]

thanks! but here we were discussing specifically the distinction between the approaches to concurrency that require you to explicitly structure your code around yield points, like async/await, and the kinds that don't, like preemptive multitasking and what i'm calling cooperative multitasking. this is unnecessarily difficult to discuss coherently if you insist on applying the term 'cooperative multitasking' indiscriminately to both, which i've shown above is in violation of established usage, and refusing to suggest an alternative term

i'll see if i can flesh out the wikipedia article a bit

[nottorp]

Where did I mix preemptive and cooperative multitasking?

And why do you think that in the case of an explicit event loop you don't have to yield? You do have to, and have to sort out some way to continue on your own. Which makes the new 'syntactic sugar' approaches much easier of course. Doesn't mean the principle isn't the same and they don't deserve the same name.

[kragen]

you didn't and i don't