Fwd: Re: Stream.limit() - puzzler/bug/feature

[Remi Forax]

On 11/16/2012 05:51 PM, Brian Goetz wrote:
>> if we provide a spliterator(), we don't need the method iterator()
>> because one can call spliterator().iterator().
>
> The idea is:
>  - If it's a serial stream, you grab an iterator() if you need direct 
> element access.
>  - If its a parallel stream, you grab a spliterator() if you need 
> direct element access.
>
>> But again, I'm not sure we should provide these methods,
>> I have no idea if it worth the pain to have to implement it for all
>> streams.
>
> There's surprisingly little pain :)
>
> Every parallel stream already has a spliterator() embedded in it; 
> that's how you create a parallel stream.  If you have a trivial pipeline:
>
>   Stream<T> pipe = foo.parallel();
>
> the library can just return the spliterator provided when the stream 
> was created.  (There are tools for turning various things like 
> Iterable or Iterator into a (dumb) Spliterator, if that's all you 
> have.)  If you have a nontrivial pipeline:
>
>   Stream<T> pipe = foo.parallel().map(e -> 3);
>
> then the library takes the base spliterator, and wraps it with one 
> whose splitting methods just pass through to the underlying 
> spliterator, and whose iterator method uses the wrapIterator methods 
> of the op chain. Painless.
>
>
> Where there is some pain is specifying it, and what the interactions 
> are with other actions.  Such as, does calling (spl)iterator mean you 
> can't call a terminal op? 

yes, asking for an iterator is a terminal op too.

> What happens when you call iterator twice?

you can't. see above :)

>   Do you get the same iterator?  What happens when you call iterator 
> and then spliterator?  But, I think we have to spec these things anyway.
>

again, when you call a terminal method, it freezes the whole streams 
chain back to the stream created with Streamable.stream(),
so you can't call a terminal ops twice otherwise you have to specify all 
combinations by example what if I call findFirst() then forEach().

Rémi