3 ms·

Can confirm. In JS, we designed `await` specifically to hide `.then()`, just as we had designed `.then()` because callbacks made tracking control flow (in part

by Yoric 1y ago

Can confirm. In JS, we designed `await` specifically to hide `.then()`, just as we had designed `.then()` because callbacks made tracking control flow (in particular errors) too complex.

psychoslave 1y ago
How is that any better to have await? Any resources I might consult on this?
- Yoric 1y ago
  Well, one of the ways we "sold" async/await it to Google was by showing how we could improve Promise-based tests. I recall that one of our test suites was tens of thousands of lines of code using `then()`. The code was complicated enough that these lines were by and large considered write-only, partly because async loops were really annoying to write, partly because error-handling was non-trivial. I rewrote that test suite using `Task.spawn` (our prototype for async/await). I don't have the exact numbers in mind, but this decreased the number of LoC by a factor of 2-3 and suddenly people could see the familiar uses of loops and `try`/`catch`.
- tsimionescu 1y ago
  Well, consider the difference between a().then(() => b()) .then(() => c()) Compared to await a() await b() await c() Even for this simple case I think it's much clearer. Then look at a more complex case: for( i=0; i<n; i++) { await a(i) ; } Now try re-writing this with then() and see the difference.
  - psychoslave 1y ago
    For the first one, it really feels like only a matter of how you break lines. Sure there is also the matter of anonymous function syntax, but The latter is more fair, here is a possible solution: const gen = (function* () { for (let i = 0; i < n; i++) yield a(i); })(); const run = next => !next.done && next.value.then(() => run(gen.next())); run(gen.next()); Or something similar using reduce. But in both cases, it illustrates the point, I guess. But if we are at point we can introduce new keywords/syntax in the language, it would just as well possible to come with something like a.chain(b, c) In case you need to pass parameters a.chain([b, p1, p2], c) And for the latter case const indexes = (function* () { for (let i = 0; i < n; i++) yield i; }) a.through(indexes)
    - Yoric 1y ago
      Well, sure, if you have `yield`, you pretty much have `await` already, as `await` is thin syntactic sugar on top of `yield` in all languages other than OCaml.

by Yoric 1y ago

Can confirm. In JS, we designed `await` specifically to hide `.then()`, just as we had designed `.then()` because callbacks made tracking control flow (in particular errors) too complex.

psychoslave 1y ago

How is that any better to have await? Any resources I might consult on this?

Yoric 1y ago
Well, one of the ways we "sold" async/await it to Google was by showing how we could improve Promise-based tests. I recall that one of our test suites was tens of thousands of lines of code using `then()`. The code was complicated enough that these lines were by and large considered write-only, partly because async loops were really annoying to write, partly because error-handling was non-trivial. I rewrote that test suite using `Task.spawn` (our prototype for async/await). I don't have the exact numbers in mind, but this decreased the number of LoC by a factor of 2-3 and suddenly people could see the familiar uses of loops and `try`/`catch`.
tsimionescu 1y ago
Well, consider the difference between a().then(() => b()) .then(() => c()) Compared to await a() await b() await c() Even for this simple case I think it's much clearer. Then look at a more complex case: for( i=0; i<n; i++) { await a(i) ; } Now try re-writing this with then() and see the difference.
- psychoslave 1y ago
  For the first one, it really feels like only a matter of how you break lines. Sure there is also the matter of anonymous function syntax, but The latter is more fair, here is a possible solution: const gen = (function* () { for (let i = 0; i < n; i++) yield a(i); })(); const run = next => !next.done && next.value.then(() => run(gen.next())); run(gen.next()); Or something similar using reduce. But in both cases, it illustrates the point, I guess. But if we are at point we can introduce new keywords/syntax in the language, it would just as well possible to come with something like a.chain(b, c) In case you need to pass parameters a.chain([b, p1, p2], c) And for the latter case const indexes = (function* () { for (let i = 0; i < n; i++) yield i; }) a.through(indexes)
  - Yoric 1y ago
    Well, sure, if you have `yield`, you pretty much have `await` already, as `await` is thin syntactic sugar on top of `yield` in all languages other than OCaml.