RFC on range design for D2

[Benji Smith]

Andrei Alexandrescu wrote:
> Andrei Alexandrescu wrote:
>> Manfred_Nowak wrote:
>>> Benji Smith wrote:
>>>
>>>> Given the use of "getNext", I think "hasNext" is a more natural
>>>> choice 
>>>
>>> clapping hands.
>>
>> Walter would love that.
>>
>> for (R r = getR(); r.hasNext; r.next) { ... }
>>
>> Look ma, no negation! Oops, I just materialized one with the 
>> exclamation sign.
> 
> I just discovered a problem with that. hasNext implies I'm supposed to 
> call next to get the thingie. It should be hasFirst, which is less 
> appealing.
> 
> Andrei

I see where you're coming from, because the range shrinks itself 
element-by-element as it iterates, eventually disappearing into a 
zero-element range.

But for me as a consumer of the container, it's a little weird.

When I visualize iteration (beware: silly metaphor ahead), it looks like 
a frog hopping from one lilly-pad to another. He might have a 
well-defined start and end point, but the lilly-pads don't evaporate 
after the frog hops away.

When I see "isEmpty" in the implementation of an iteration routine, it 
makes me think of a producer/consumer work queue. The list is only empty 
if the consumer has consumed all the work items from the queue.

I get what you're saying about the iteration-range being empty because 
it shrinks itself during each step of the iteration. But to me, 
iteration is an idempotent operation, so something non-empty before the 
iteration should not be empty after the iteration.

--benji