> Is it possible to have a yield inside a called function (i.e., not the generator function itself)?
Call a generator function from a generator function? Sure, you just need to transitively yield its content using `yield* [[expr]]` (which delegates part of the iteration to the `expr` generator)
const res = fetch('https://api.github.com/orgs/facebook'); // yield here
actually requires a "yield" in front of the "fetch"? But what if I want the fetch() function to decide whether to yield or not?
Of course, fetch(), could yield a status specifying whether its calling-ancestors should yield, but this can become unwieldy very quickly, and might require an exception mechanism of its own. Better to just let called functions yield.
In javascript it would yes (actually a `yield*`, or an `await` in async/await). With native coroutines it wouldn't (the runtime would implicitly yield on IO).
> But what if I want the fetch() function to decide whether to yield or not?
In javascript? The question doesn't really make sense, a function is either sync or async.
> The question doesn't really make sense, a function is either sync or async.
Well, either fetch() blocks, or not. If it blocks, then it should yield, its caller should yield, etc. If it doesn't block, then it can just run to completion.
Don't elide important parts of the quote. In javascript your question doesn't make sense.
> Well, either fetch() blocks, or not.
Javascript functions always block.
> If it blocks, then it should yield, its caller should yield, etc. If it doesn't block, then it can just run to completion.
If a function is async, you must yield[0]. It may not need* that capability (conditionally) and doesn't have to yield at all e.g.
function*() {
return 4;
}
is valid and will not suspend. You must still yield*[0] on it so that it is properly resolved as a generator.
[0] I think that's not an issue for async/await as it's syntactic sugar for then chains, the code itself may be converted to a generator or whatever but it will embed the driver
Call a generator function from a generator function? Sure, you just need to transitively yield its content using `yield* [[expr]]` (which delegates part of the iteration to the `expr` generator)