Axel Rauschmayer schrieb:
Right, it doesn’t look like one needs to know the returned value when
forwarding `return()`.
Yeah, to support the iterator protocol as yield* does it one would need
to forward that value. That might be another good use case for a meta
property. However, I haven't really grasped what the value is used for,
so I guess passing `undefined` is just fine.
But: you need to guard against other ways of reaching `finally`.
Why? I intended to always reach finally, and always close the iterator.
Also, simplicity ftw :-)
> That’s not what all the other constructs in ES6 do: they only call
`return()` if iteration stops abruptly.
Only because all the other constructs in ES6 try to exhaust the
iterator. And when it's finished anyway, one doesn't need to close it.
There is in fact no problem with calling `.return()` too often, it just
doesn't do anything to completed generators.
Btw, your `take` function is the perfect example where a non-exhausted
iterator *should* be closed as return prematurely - like a `break` in a
for-of loop would.
Also missing from this code: checking whether the iterator actually has the
methods `return()` and `throw()` and responding accordingly.
Yupp, that might need to be added as well. However, the current
behaviour (without the `forwardReturn = false`) is not that bad: If
`throw` doesn't exist, it tries the `return` from the finally case
before throwing a type error.
To implement it correctly, I guess it should be
try {
while (--n > 0) {
var {done, value} = iterator.next();
if (done) return item.value;
yield item.value;
}
} catch (e) {
if (typeof iterator.throw == "function") {
iterator.throw(e);
done = true;
} else
throw e;
} finally {
if (!done)
iterator.return();
}
Bergi
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