[catern]

I totally agree with your framing of the value of async/await, but could you elaborate more on why you think that this behavior (which I would call "cooperative concurrency") is important for (ocap?) RPC systems? It seems to me that preemptive concurrency also suffices to make RPC viable. Unless you just feel that preemptive concurrency is too hard, and therefore not workable for RPC systems?

[kentonv]

Almost all ocap systems seem to use event loops -- and many of the biggest ocap nerds I know are also the biggest event loop nerds I know. I'm not actually sure if this is a coincidence or if there's something inherent that makes it necessary to pair them.

But one thing I can't figure out: What would be the syntax for promise pipelining, if you aren't using promises to start with?

[catern]

>What would be the syntax for promise pipelining, if you aren't using promises to start with?

Oh, great point! That does seem really hard, maybe even intractable. That's definitely a reason to like cooperative concurrency, huh...

Just to tangent even further, but some ideas:

- Do it the ugly way: add an artificial layer of promises in an otherwise pre-emptive, direct-style language. That's just, unfortunately, quite ugly...

- Use a lazy language. Then everything's a promise! Some Haskell optimizations feel kind of like promise pipelining. But I don't really like laziness...

- Use iterator APIs; that's a slightly less artificial way to add layers of promises on top of things, but still weird...

- Punt to the language: build an RPC protocol into the language, and promise pipelining as a guaranteed optimization. Pretty inflexible, and E already tried this...

- Something with choreographic programming and modal-types-for-mobile-code? Such languages explicitly track the "location" of values, and that might be the most natural way to represent ocap promises: a promise is a remote value at some specific location. Unfortunately these languages are all still research projects...