Grouping stream elements by their position - how to handle tail of stream ?

[Zhong Yu]

On Sat, Feb 2, 2013 at 2:59 PM, Lattie <latsama at gmail.com> wrote:
> Boaz,
>
> I just wanted to validate your request as I ran into *exactly* the
> same issue yesterday.
>
> I think that explode ought to call some sort of finalizer method at
> end of stream to accommodate those BiBlocks which are stateful.
>
> Also, I'm not sure if 'explode' is the best name as I find I am using
> it more generally to transform a stream of X into a stream of Y, where
> Y may require 1 or more X's as inputs.  (I didn't find any other
> method that enabled that type of transformation.  Please feel free to
> educate me :)

I also wanted this. It's kind of like a lexer that turns a char stream
into a token stream; an EOF event needs to be raised and handled.

However, it is inherently sequential, which Stream doesn't want to
support, even though it is teasingly named *stream*. Someone will
invent other models like Sequence - fortunately the only reason we
didn't have these things is the syntax of anonymous class, which is
now solved by lambda expression.

Zhong Yu

>
>
>
>
>
>
> On Sat, Feb 2, 2013 at 12:35 PM, Boaz Nahum <boaznahum at gmail.com> wrote:
>> Hi.
>>
>> I looking in Stream interface for a way to convert a stream of
>>    {  t1, t2, .. Tn }
>> to
>>    { {t1,t2}, ... {Tn-1, Tn} }
>> or
>>    { {t1,t2}, ... {Tn, null}}
>>
>> Lets assume {t1, t2} are aggeraget by Pair<T,T>
>>
>>
>>
>> So I tried to use explode:
>>
>> *        Stream<Integer> si = Arrays.asList(1, 2, 3, 4, 5).stream();
>>
>>         Stream<Pair<Integer, Integer>> spi = si.sequential().explode(new
>> BiConsumer<Stream.Downstream<Pair<Integer, Integer>>, Integer>() {
>>
>>             Integer firstValue;
>>
>>             @Override
>>             public void accept(Stream.Downstream<Pair<Integer, Integer>>
>> pairDownstream, Integer v) {
>>
>>                 if (firstValue == null) {
>>                     firstValue = v;
>>                 } else {
>>
>>                     pairDownstream.send(new Pair<>(firstValue, v));
>>                     firstValue = null;
>>
>>                 }
>>             }
>>
>>         });
>> *
>>
>> But I didn't find a way to add the tail of input stream {.., 5} to the new
>> stream { ,,, {5, null}}.
>>
>> Of-course this only simplified example of more general problem I have.
>>
>> Thanks
>> Boaz
>>
>