It refers to Trio nurseries as “scopes”. I thought about them like that for a while, but don’t think that’s not exactly the right view now. As a subroutine, you can’t (usually) reach up into your parent static or dynamic scopes and cause new objects to be created there and outlive your own dynamic extent. (Tcl exempted.)
Because nurseries are first-class objects, though, you’re free to create a root nursery at startup and stick it in a global variable, after which everyone is free to create as many Go-style unaccountable threads as they want to. It’s just that you don’t have to. Yet passing worker threads their originating nursery so that they can spawn more peer workers is a moderately useful pattern.
TL;DR: Firsr-class nurseries are not quite scopes because they don’t enforce strict lifetime nesting between a spawned thread and the thread that caused it to be spawned.
When I read the Go statement considered harmful post, I felt the same thing. This just makes sense, everything should be like this. A number of these ideas have been designed into Kotlin’s concurrency library, what are your thoughts about it?
I haven't seen Kotlin's library, so I can't comment.
Do you have a link? I wasn't able to pull up anything good with a search.
To answer the GGP, this looks like true structured concurrency to me. Chalk one up for Kotlin!
Not really. I've had people you after me for such things.
Definitely a good thing. But does that really justify the label "structured concurrency"? I was rather hoping to see something more, especially since languages like Rust, Go, JavaScript (and even Python) go much further.
The entire point of structured concurrency or structured programming is to build limitations into the system, then build other guarantees on those limitations. If you don't have the limitations, you don't have the things you can build on it. Systems lacking those limitations do not "go beyond" the limitations, they lack the ability to build the guarantees.
I have been influenced in my Go programming by this essay. A lot of my concurrency is actually "structured concurrency" if you look at it. But you have to look at it to see, because there is no way for me to guarantee it structurally. No matter how much I use the ideas, no matter how much I were to write it into an API, I can never prevent anything from blasting a "go" statement whereever they want, whenever they want, and violating the limitations, and thus breaking the guarantees. This is not the end of the world some programmers treat it as; no language can do everything and enforce everything and be perfect without the programmer having to bring some discipline to the party. But neither is it no big deal at all and something you can just wave away with a vague statement about how some programmers just need to be better programmers or something. These things matter.
It's interesting to see this posted after three years.
In fact, there should be "(2019)" in the Hacker News title.
After looking at the definition, I think it holds up well. I would probably tweak it, but I was three years less experienced back then.
It's weird to think that I posted that just two months before lockdown. It seems like I posted it long before that...