Think about `flatMap` (which filter is a special case of), this is one-to-many function that can also return 1 or 0 elements for each input. So it makes sense to include 0 as "many".
Filter isn't many-to-... At all, at no point it collapses a subsequence of elements, it only works on one element at a time On Sun, 7 Apr 2024, 19:31 Ernie Rael, <err...@raelity.com> wrote: > On 24/04/07 9:11 AM, Viktor Klang wrote: > > Hi Ernie, > > "Many" in this case refers to "N", which is "0 ... N", > > OK, I was wondering about "many" including "0". > > so I'd say while it is techincally correct as-is, perhaps more precise > would be to say "1-to-0..1" gatherer, since for every element in, there is > 0 or 1 element out. > > I see. > > > Many-to-one would be 0..N -> 1, which means that an empty input would > > "could" not "would"? > > yield a single output. > > Out of curiosity, is either correct technically? > > > Other than at initialization or finish, is it possible to have an "empty" > input? > > > -ernie > > > Cheers, > √ > > > *Viktor Klang* > Software Architect, Java Platform Group > Oracle > ------------------------------ > *From:* core-libs-dev <core-libs-dev-r...@openjdk.org> > <core-libs-dev-r...@openjdk.org> on behalf of Ernie Rael > <err...@raelity.com> <err...@raelity.com> > *Sent:* Sunday, 7 April 2024 18:06 > *To:* core-libs-dev@openjdk.org <core-libs-dev@openjdk.org> > <core-libs-dev@openjdk.org> > *Subject:* JEP 473: Stream Gatherers (Second Preview) > > > This is about what might be a minor doc issue. > > In https://openjdk.org/jeps/473 it says > > As another example, Stream::filter takes a predicate that determines > whether an input element should be passed downstream; this is simply a > stateless one-to-many gatherer. > > Shouldn't this be "many-to-one"? > > -ernie > > >
