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Exactly. The way I think about it, the "async" keyword transforms function code so that local variables are no longer bound to the stack, making it possible to

Exactly. The way I think about it, the "async" keyword transforms function code so that local variables are no longer bound to the stack, making it possible to pause function execution (using "await") and resume it at an arbitrary time. Performing that transformation manually is a fair amount of work and it's prone to errors, but that's what we did when we wrote cooperatively multitasked code.

nottorp 3y ago
> when we wrote cooperatively multitasked code That's my point, we still do that. And based on your phrasing we're forgetting it :)
- hathawsh 3y ago
  Sure, that's a good way to look at it. Another way to look at it: because the process of transforming code for cooperative multitasking is now much cleaner and simpler, it's fine to use new words to describe what to do and how to do it.
  - kragen 3y ago
    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 3y ago
      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 3y ago
        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/Carbon/Conceptual/Multitasking_MultiproServ/02concepts/concepts.html 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/350723/what-is-the-yield-functionality-in-windows-3-11 https://softwareengineering.stackexchange.com/questions/3507... https://retrocomputing.stackexchange.com/questions/791/how-did-windows-3-1-implement-multitasking 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 https://news.ycombinator.com/item?id=38861074

nottorp 3y ago

> when we wrote cooperatively multitasked code That's my point, we still do that. And based on your phrasing we're forgetting it :)

hathawsh 3y ago
Sure, that's a good way to look at it. Another way to look at it: because the process of transforming code for cooperative multitasking is now much cleaner and simpler, it's fine to use new words to describe what to do and how to do it.
- kragen 3y ago
  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 3y ago
    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 3y ago
      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/Carbon/Conceptual/Multitasking_MultiproServ/02concepts/concepts.html 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/350723/what-is-the-yield-functionality-in-windows-3-11 https://softwareengineering.stackexchange.com/questions/3507... https://retrocomputing.stackexchange.com/questions/791/how-did-windows-3-1-implement-multitasking 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 https://news.ycombinator.com/item?id=38861074