Sized

[Kevin Bourrillion]

I think you're implying that size() doesn't make sense for such an
Iterable. Correct?

But why not? You're describing an (imho sociopathic, but that's beside the
point) iterable that is content to be destroyed upon a single use. Calling
size() would just be one of the ways to use it and destroy it. I see
nothing inconsistent about that.

While it probably seems like I'm just trying to be a pain -- probably seems
a *lot* like that -- all I'm after is some clear way to explain the purpose
of this new type, that makes it make sense to people when they should use
it and when they shouldn't. I'm asking questions to understand this
rationale so that I can explain it myself. But I'm just not following it
yet.


On Mon, Nov 5, 2012 at 3:15 PM, Brian Goetz <brian.goetz at oracle.com> wrote:

> Iterable doesn't guarantee that you can iterate the source more than once.
>  It is entirely consistent with the Iterable spec that iterator() always
> returns the same Iterator.
>
> On Nov 4, 2012, at 10:31 AM, Kevin Bourrillion wrote:
>
> On Fri, Nov 2, 2012 at 3:53 PM, Brian Goetz <brian.goetz at oracle.com>wrote:
>
> I think you're focusing on another problem.  These things *have* size()
>> methods already; I'm trying to capture this in a finer-grained interface.
>>  The "size in O(1) time" is a whole orthogonal concern.
>>
>
> Sorry -- I was just going off the initial description, "It is useful to
> indicate that an aggregate knows its size."  If the real goal instead is
> only to distinguish when an aggregate "decides to expose a size() operation
> for *whatever* reason", then right, there's no problem here.
>
> But this new understanding doesn't make clear the reason why Iterable
> shouldn't go ahead and extend Sized as well. As Mike says, it "can
> determine it's size and that size() implementation is at least as good as
> getting an iterator and counting the items" -- that's undeniably the case.
> And as you say, the performance question is orthogonal.
>
> But I think you don't want that, so I am still missing what the
> distinction between Sized and not Sized is supposed to be.
>
>
> --
> Kevin Bourrillion | Java Librarian | Google, Inc. | kevinb at google.com
>
>
>


-- 
Kevin Bourrillion | Java Librarian | Google, Inc. | kevinb at google.com