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Here I'm a bit out of my depth. I think with Erlang you don't need to know >that particular implementation of green threads, but you need to implement the requ

Here I'm a bit out of my depth. I think with Erlang you don't need to know >that particular implementation of green threads, but you need to implement the required specifics of the VM FFI (which in practical terms might be what you meant) - but this has a reason, in that, for the VM to provide its guarantees it needs to be able to count "cycles", refs, etc in order to preempt the execution of any function/process at given points, so that no single process can block the scheduler. It also needs to transform things from and into data types usable inside the VM. I think you can also use "dirty" nifs, but here you might crash the VM so you really need to know what you're doing (and you still have to translate things to and from the vm). And there's also ports, and C Nodes. These have a higher sync cost but can be treated by the VM as if they were processes/erlang nodes. Lastly, you can also just shell from the VM to an OS level process, or use sockets, etc. But I doubt this is anything 99% of the people writing JS do in JS? One of the things people using Elixir or Erlang is exactly because of the guarantees and programming model of the VM. Again, might be missing what you mention because it's not an area I have explored in any meaningful way.

int_19h 6y ago
That's the thing - it works for Erlang/Elixir, because it tends to live in its own ecosystem with its own libraries etc. If you are working on something where there's an existing large ecosystem in, say, C++, you'll be reinventing the wheel. Or jumping through hoops with a multiprocess implementation (pipes, sockets etc), and having fun synchronizing those. Now, not all projects are like that - but reusing libraries from other languages is common enough in large projects. Thus, languages that can't accommodate that use case, don't become truly mainstream. Within their niche, they can be much more pleasant to work with, though. So I don't think there's anything wrong with Elixir per se, and for some tasks, it makes perfect sense - but it's not a very general-purpose tool. Note, by the way, that I'm not talking just (or even mostly!) about JS, but rather about async/await in general - e.g. also in C#, where that syntax originated, or these days in C++20. On Windows, if you write "modern" (UWP) apps, regardless of the language used, they make a lot of async API calls for stuff like UI - and the implementation is all in native code, running in the same process as your app.
- hnedeotes 6y ago
  Yeah, it kinda limits the scope of adoption/interest in a way and I think everybody working with it would like that it wasn't the case but I don't think that gap can be worked out easily (or in a practical way) because without the code being written to accommodate the requirements of the VM it can't do what it's meant to do. If you link a piece of code that can crash the whole VM or steal the processors schedulers then the value in writing supervision trees, restart strategies, compartmentalising your runtime concerns into processes, plus the tradeoffs made in the vm/language design themselves go down, because a single invocation can throw it all out of the window. (and note, this is not to say the "outside" code is of less quality or anything, is just that when writing "inside" the vm, if you don't account for an unknown problem that happens only sometimes but place it under a proper chain of supervision (and this is much easier to do than writing 100% bug-free I've covered all cases including heinsenbugs code), it will be contained and not bring down the entire VM along with everything it was doing at the time, like all open client sockets or work it was doing, or impact other users when it happens)

int_19h 6y ago

That's the thing - it works for Erlang/Elixir, because it tends to live in its own ecosystem with its own libraries etc. If you are working on something where there's an existing large ecosystem in, say, C++, you'll be reinventing the wheel. Or jumping through hoops with a multiprocess implementation (pipes, sockets etc), and having fun synchronizing those. Now, not all projects are like that - but reusing libraries from other languages is common enough in large projects. Thus, languages that can't accommodate that use case, don't become truly mainstream. Within their niche, they can be much more pleasant to work with, though. So I don't think there's anything wrong with Elixir per se, and for some tasks, it makes perfect sense - but it's not a very general-purpose tool. Note, by the way, that I'm not talking just (or even mostly!) about JS, but rather about async/await in general - e.g. also in C#, where that syntax originated, or these days in C++20. On Windows, if you write "modern" (UWP) apps, regardless of the language used, they make a lot of async API calls for stuff like UI - and the implementation is all in native code, running in the same process as your app.

hnedeotes 6y ago
Yeah, it kinda limits the scope of adoption/interest in a way and I think everybody working with it would like that it wasn't the case but I don't think that gap can be worked out easily (or in a practical way) because without the code being written to accommodate the requirements of the VM it can't do what it's meant to do. If you link a piece of code that can crash the whole VM or steal the processors schedulers then the value in writing supervision trees, restart strategies, compartmentalising your runtime concerns into processes, plus the tradeoffs made in the vm/language design themselves go down, because a single invocation can throw it all out of the window. (and note, this is not to say the "outside" code is of less quality or anything, is just that when writing "inside" the vm, if you don't account for an unknown problem that happens only sometimes but place it under a proper chain of supervision (and this is much easier to do than writing 100% bug-free I've covered all cases including heinsenbugs code), it will be contained and not bring down the entire VM along with everything it was doing at the time, like all open client sockets or work it was doing, or impact other users when it happens)