Am I the only one who finds it incredibly hard to grok how async/await and "regular" sequential code interplay? In JavaScript I strongly prefer the regular Promise way of doing things because async feels like it's mixing metaphors. Being relatively new to Rust it's not totally clear to me whether the Futures example in the article could be made more readable - it's definitely pretty gross - but I have to wonder.
It took me a while to get comfortable with it too. The intuition I use is that in the past it used to be DrawWindow(), DrawWindow(), DisplayResultsofSlowFunction() and then the window would freeze for a few seconds, but with async/await theres a queue basically and your DisplayResultsOfSlowFunction() gets put to the side while awaiting so DrawWindow() can keep doin what its doin and your app doesnt appear to freeze, for a gui example (idk if that helps or if ye already knew it but just in case, for me all the internet explanations never talked about the scheduler for some reason so it took me a while).
Note that futures, promises, &c. are all about deliberately asynchronous operations, most commonly I/O. Expressed in older terms, it’s cooperative multitasking.
Thus, when you have a CPU-bound function, they are of no assistance in UI responsiveness, unless you deliberately insert yield points; in JavaScript, for example, you might do a unit of work, or process work until, say, ten milliseconds have elapsed, and then call setTimeout(keepGoing, 0). (Critically in JavaScript, you mustn’t use `Promise.resolve().then(keepGoing)`, because that’ll end up in the microtask queue which must be flushed empty before the browser will render, so you won’t actually yield to the UI with this approach.)
So be careful about your DisplayResultsOfSlowFunction(). If its slowness is that it takes a long time to calculate, and it doesn’t actually have any asynchronous stuff in it, async will not help you.
I understand how they work. It's just that turning something as fundamental as "each semicoloned statement happens after the previous one, as quickly as possible", into an abstraction, makes me really uncomfortable.
It's different in a statically-typed language. The compiler and editor tooling keeps you aware at all times of that interplay. If you forget, you're reminded rather quickly.
