Bifurcate Sent from my iPhone
> On Jun 18, 2018, at 6:29 PM, Brian Goetz <brian.go...@oracle.com> wrote: > > "bisecting" sounds like it sends half the elements to one collector and half > to the other ... > > "tee" might be a candidate, though it doesn't follow the `ing convention. > "teeing" sounds dumb. > > > >> On 6/15/2018 7:36 PM, Paul Sandoz wrote: >> Hi Tagir, >> >> This is looking good. >> >> My current favorite name for the factory method is “bisecting” since we are >> dividing the collector into two collectors, the results of which are then >> merged. >> Suggested first paragraph of the factory method: >> >> "Returns a collector that passes the input elements to two specified >> collectors and merges their results with the specified merge function.” >> >> Paul. >> >>> On Jun 15, 2018, at 4:26 AM, Tagir Valeev <amae...@gmail.com> wrote: >>> >>> Hello! >>> >>> I created a preliminary webrev of my own implementation (no testcases yet): >>> http://cr.openjdk.java.net/~tvaleev/patches/pairing/webrev/ >>> If anybody wants to sponsor my implementation, I will happily log an issue >>> and write tests. >>> >>> The name "pairing" was invented by me, but as I'm not a native English >>> speaker I cannot judge whether it's optimal, so better ideas are welcome. >>> Also I decided to remove accumulator types from public type variables. They >>> do not add anything to type signature, only clutter it >>> increasing the number of type parameters from 4 to 6. I think it was a >>> mistake to expose the accumulator type parameter in other cascading >>> collectors >>> like filtering(), collectingAndThen(), groupingBy(), etc. I'm not insisting >>> though, if you feel that conformance to existing collectors is >>> more important than simplicity. >>> >>> With best regards, >>> Tagir Valeev. >>> >>>> On Fri, Jun 15, 2018 at 5:05 AM Brian Goetz <brian.go...@oracle.com> wrote: >>>> >>>> Well, I don't see the need to pack the two results into a Map.Entry >>>> (or any similar) container as a drawback. >>> From an "integrity of the JDK APIs" perspective, it is unquestionably a >>> drawback. These items are not a Key and an associated Value in a Map; >>> it's merely pretending that Map.Entry really means "Pair". There's a >>> reason we don't have a Pair class in the JDK (and no, let's not reopen >>> that now); using something else as a Pair proxy that is supposed to have >>> specific semantics is worse. (It's fine to do this in your own code, but >>> not in the JDK. Different standards for code that has different audiences.) >>> >>> Tagir's proposed sidestepping is nice, and it will also play nicely with >>> records, because then you can say: >>> >>> record NameAndCount(String name, int count); >>> >>> stream.collect(pairing(collectName, collectCount, NameAndCount::new)); >>> >>> and get a more properly abstract result out. And its more in the spirit >>> of existing Collectors. If you want to use Map.Entry as an >>> _implementation detail_, that's fine. >>> >>> I can support this form. >>> >>>> I also don't see a larger abstraction like BiStream as a natural fit >>>> for a similar thing. >>> I think the BiStream connection is mostly tangential. We tried hard to >>> support streams of (K,V) pairs when we did streams, as Paul can attest, >>> but it was a huge complexity-inflater and dropping this out paid an >>> enormous simplification payoff. >>> >>> With records, having streams of tuples will be simpler to represent, but >>> no more performant; it will take until we get to value types and >>> specialized generics to get the performance we want out of this. >>> >>> >
