Spliterator

[Joe Bowbeer]

The spec for getSizeIfKnown() seems similar to that of
InputStream.available(), which is spec'd so loosely that I don't think it
should ever be used.  Similar to Thread.yield() in that respect.



On Mon, Nov 19, 2012 at 12:37 PM, Doug Lea <dl at cs.oswego.edu> wrote:

> On 11/16/12 11:40, Brian Goetz wrote:
>
>> Following up...we've eliminated StreamAccessor from the design, so you
>> only need
>> a Spliterator (and maybe stream flags) now to create a stream.  Here's the
>> latest API and spec for Spliterator.  Some explanations of the choices
>> are in
>> the original mail to which this is a reply.
>>
>
> My main concern is spec'ing/using the heuristic methods that
> could do anything and return any answer vs provide required
> functionality.
>
> For example, getSizeIfKnown(). Is it required to promise that the
> size will not change after return? Is it required to provide a result
> if one is computationally possible rather than just handy?
> Is it required to lie and return Integer.MAX_VALUE if it overflows int?
> (Reminder: HashMaps and CHMs with > 1 << 31 elements are known to
> exist out there.) These will be hard to spec exactly right.
> And there are 4 more methods like this.
>
> And I'm left wondering (as always) just how much good these
> methods will do compared to an ultra-small/simple API,
> considering that most collection developers would rather
> put more time into writing custom versions of forEach, reduce,
> etc rather than tuning their Spliterator hinting methods so that
> the lambda-libs default versions work well?
>
> Or, considering that each of these added methods seems
> targeted at a particular data structure/shape (array,
> tree, bounded list/seq), why not make subinterfaces for them?
>
> interface Spliterator
> interface SizedSpliterator extends Spliterator...
> interface RandomAccessSpliterator extends SizedSpliterator ...
> etc
>
> On a little thought, I can't think of a reason not to do this?
> Can you?
>
> (Where to get this started, the minimal base version of
> Spliterator has a split() method returning one with fewer
> elements or null if it can't, and either is a or returns
> an Iterator.)
>
> -Doug
>
>