For reference, in my iterative proposal, I've been considering adding a
`.finished()` method to the Fuse adaptor, which would let you easily add that
capability to any iterator.
-Kevin Ballard
> On Aug 11, 2013, at 6:47 PM, Daniel Micay <danielmi...@gmail.com> wrote:
>
>> On Sun, Aug 11, 2013 at 6:32 PM, Tom Lee <rust-...@tomlee.co> wrote:
>>
>>> On Sun, Aug 11, 2013 at 3:18 PM, Jens Nockert <j...@nockert.se> wrote:
>>>
>>>
>>> On 12 Aug 2013, at 00:09, Tom Lee <rust-...@tomlee.co> wrote:
>>>
>>> Anyway, this sort of confusion is exactly why I don't like for..else. But
>>> then maybe I'm the only one that's confused here. :)
>>>
>>>
>>> Obviously you were not the only one, since there was a long thread without
>>> clarification.
>>>
>>> While I think it is reasonably clear (since I am used to it), I don't
>>> think it is more clear than something like (in faux pyrust)
>>>
>>> let iterations = xrange(100);
>>>
>>> for i in iterations {
>>> …
>>> if converged {
>>> break;
>>> }
>>> }
>>>
>>> if iterations.finished() {
>>> fail!("Oh noes, it did not converge");
>>> }
>>
>> I really like this. There's no room for confusion here.
>
> The iterator adaptors don't keep track of whether they've finished,
> they only bubble up the underlying `next()` calls. The `None` will be
> returned during the loop, and after that there's no way to query
> whether it has finished.
>
> For example, this is zip:
>
> fn next(&mut self) -> Option<(A, B)> {
> match (self.a.next(), self.b.next()) {
> (Some(x), Some(y)) => Some((x, y)),
> _ => None
> }
> }
>
> There's a separate thread about this, but I don't think returning
> `None` forever without side effects is a guarantee we should make.
> Python does not make the guarantee, and the functions like `zip` there
> will continue calling the underlying iterators.
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