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I'm surprised Rust went with a Scala-inspired async/await considering it wasn't well-liked outside of PLT enthusiasts. JavaScript adopted it as I don't think yo

I'm surprised Rust went with a Scala-inspired async/await considering it wasn't well-liked outside of PLT enthusiasts. JavaScript adopted it as I don't think you could bolt any other type of sugar on top of the event loop in browsers... but Rust shouldn't suffer from such baggage.

nynx 6y ago
What's an alternative to async/await that's explicit about runtime costs?
- thu2111 6y ago
  How explicit do you want? The loom model is VM managed thread stacks with user space context switching. The costs are all quantifiable and a suspended "virtual" thread uses memory directly proportional to the amount of stuff on the stack, same as any coro implementation. However there is no async/await or coloured functions. The VM just makes threads super cheap
  - roca 6y ago
    Rust started off with user ("green") threads. The problem is interop with other code via FFI --- it gets really painful and potentially expensive. That's not good for a systems language. So they ripped it out.
pshc 6y ago
Do you have a source on people generally disliking async/await? I've become a fan of it in JS.
- spamizbad 6y ago
  There's the function coloring issue: https://journal.stuffwithstuff.com/2015/02/01/what-color-is-your-function/ https://journal.stuffwithstuff.com/2015/02/01/what-color-is-... Where your sync functions have X considerations and your async functions have separate Y considerations - BUT, async/await sugar makes these widely different behaviors look nearly identical - so you get "clean" sync code aesthetics on your asynchronous code and are sort of on your own when tracking the behavior of its implication.
xiphias2 6y ago
Rust was the first language that made it efficient, abstraction without overhead (which took many years of work). It’s just a state machine with an enum holding the state, but of course it means that the memory model is harder to understand than with JavScript.
roca 6y ago
C# and C++ adopted basically the same model.
- CodeArtisan 6y ago
  Note that C++ offers async as a library and not as a programming language feature which Bjarne Stroustrup is strongly against. He talk more about why in "The Design and Evolution of C++" but i don't have the material at hand. As far as i remember, his main argument was that there is no concurrency model to fit them all and thus it doesn't worth to add new syntax and semantics for a specific model except to make the PL more complex and harder to implement.
  - roca 6y ago
    The main piece is stackless coroutines which definitely aren't a library.
  - xfer 6y ago
    No without compiler support you can't do async in a library. Rust also does async in library so to speak.
  - jcelerier 6y ago
    > Note that C++ offers async as a library and not as a programming language feature which Bjarne Stroustrup is strongly against. https://www.modernescpp.com/index.php/c-20-coroutines-the-first-overview https://www.modernescpp.com/index.php/c-20-coroutines-the-fi...
    - tick_tock_tick 6y ago
      coroutines themselves have nothing todo with async/await.
      - jcelerier 6y ago
        I wonder what that co_await keyword is for then
blackoil 6y ago
Isn't async/await from F#/C# world, or Scala has a different variant?
kelnos 6y ago
I'm confused... Scala doesn't have async/await.

nynx 6y ago

What's an alternative to async/await that's explicit about runtime costs?

thu2111 6y ago
How explicit do you want? The loom model is VM managed thread stacks with user space context switching. The costs are all quantifiable and a suspended "virtual" thread uses memory directly proportional to the amount of stuff on the stack, same as any coro implementation. However there is no async/await or coloured functions. The VM just makes threads super cheap
- roca 6y ago
  Rust started off with user ("green") threads. The problem is interop with other code via FFI --- it gets really painful and potentially expensive. That's not good for a systems language. So they ripped it out.

pshc 6y ago

Do you have a source on people generally disliking async/await? I've become a fan of it in JS.

spamizbad 6y ago
There's the function coloring issue: https://journal.stuffwithstuff.com/2015/02/01/what-color-is-your-function/ https://journal.stuffwithstuff.com/2015/02/01/what-color-is-... Where your sync functions have X considerations and your async functions have separate Y considerations - BUT, async/await sugar makes these widely different behaviors look nearly identical - so you get "clean" sync code aesthetics on your asynchronous code and are sort of on your own when tracking the behavior of its implication.

xiphias2 6y ago

Rust was the first language that made it efficient, abstraction without overhead (which took many years of work). It’s just a state machine with an enum holding the state, but of course it means that the memory model is harder to understand than with JavScript.

roca 6y ago

C# and C++ adopted basically the same model.

CodeArtisan 6y ago
Note that C++ offers async as a library and not as a programming language feature which Bjarne Stroustrup is strongly against. He talk more about why in "The Design and Evolution of C++" but i don't have the material at hand. As far as i remember, his main argument was that there is no concurrency model to fit them all and thus it doesn't worth to add new syntax and semantics for a specific model except to make the PL more complex and harder to implement.
- roca 6y ago
  The main piece is stackless coroutines which definitely aren't a library.
- xfer 6y ago
  No without compiler support you can't do async in a library. Rust also does async in library so to speak.
- jcelerier 6y ago
  > Note that C++ offers async as a library and not as a programming language feature which Bjarne Stroustrup is strongly against. https://www.modernescpp.com/index.php/c-20-coroutines-the-first-overview https://www.modernescpp.com/index.php/c-20-coroutines-the-fi...
  - tick_tock_tick 6y ago
    coroutines themselves have nothing todo with async/await.
    - jcelerier 6y ago
      I wonder what that co_await keyword is for then

blackoil 6y ago

Isn't async/await from F#/C# world, or Scala has a different variant?

kelnos 6y ago

I'm confused... Scala doesn't have async/await.