Hi Tagir, "Let a thousand flowers bloom” :-) It’s great you can do this.
For the moment i am ok with waiting until we have better mechanisms in the language platform to do even better [*], then we can gather use-cases based on developer experience such as yours. Paul. [*] FWIW we experimented a couple of times with a Map/BiStream abstraction, and each time decided to back away. > On 7 Nov 2015, at 05:49, Tagir F. Valeev <amae...@gmail.com> wrote: > PS> In other cases e.g. about preceding elements, a > PS> history-based wrapping spliterator could work (IIRC Jose Paumard > PS> has presented such examples), but we are currently lacking an SPI > PS> to plug-in operations, so one needs to directly use the > Stream.spliterator escape. > > Actually I wrote a spliterator in my StreamEx library which allows to > process pairs of input elements (along with primitive > specializations), of course using Stream.spliterator escape (which is > not that bad if you avoid tryAdvance call): > https://github.com/amaembo/streamex/blob/master/src/main/java/javax/util/streamex/PairSpliterator.java > Despite it's not lock-free, it greatly parallelizes and has good > overall performance, so I'm somewhat proud of it. It allows to solve > many interesting problems. > > Pairwise differences: > int[] diff = IntStreamEx.of(intArray).pairMap((a, b) -> b-a).toArray(); > > Skip last stream element: > Stream<T> stream = StreamEx.of(input).pairMap((a, b) -> a); > > Check if input is sorted: > StreamEx.of(input).pairMap(Comparable::compareTo).allMatch(r -> r <= 0); > > Find first misplaced element: > StreamEx.of(input).pairMap((a, b) -> a.compareTo(b) > 0 ? b : > null).nonNull().findFirst(); > > More complex example: sort word list and add header before each letter: > StreamEx.of(words).sorted() > .prepend(" ") // Stream.concat(Stream.of(" "), this) > .pairMap((a, b) -> a.charAt(0) == b.charAt(0) ? Stream.of(b) : > Stream.of("Words starting with letter "+b.substring(0,1), b)) > .flatMap(Function.identity()) > .forEach(System.out::println); > > And so on. It would be great to see such feature in JDK as well! >
