Hacker News Reader

Comment by seabrookmx | Hacker News Reader

It's odd that the async/await syntax _exclusively_ uses threads under the hood. I guess it makes for a straightforward implementation, but in every language I've seen the point of async/await is to use an event loop/cooperative multitasking.

View on HN

I’d say that the point of async/await is to create a syntax demarcation between functions which may suspend themselves (or be suspended by a supervisory system) and those functions that process through completely and cannot be suspended (particularly by a supervisory system). The means to enable the suspension of computation and allow other computations to proceed following that suspension are implementation details.

So, having an async function run on a separate thread from those functions that are synchronous seems a viable way to achieve the underlying goal of continuous processing in the face of computations that involve waiting for some resource to become available.

I will agree that inspired by C#’s originating and then JavaScripts popularization of the syntax, it is not a stretch to assume async/await is implemented with an event loop (since both languages use such for implementation).

Noob question: if it just compiles to threads, is there any need for special syntax in the first place? My understanding was that no language support should be required for blocking on a thread.

Async/await should do a little more under the hood than what the typical OS threading APIs provide, for example forwarding function parameters and return values automatically instead of making the user write their own boilerplate structs for that.

One advantage is that it gives you the opportunity to move to a more sophisticated implementation later without breaking backwards compatibility (assuming the abstraction does not leak).

Reply on news.ycombinator.com