Add takeUntil operator about lightweight-stream-api

[aNNiMON]

I think, it is impossible in Stream API. In rxjava we can compare items in two Observables according to the emit time, but in Stream API there is no time. If two Streams has items, we can take them at any time.

[dalewking]

Sorry, linked to the wrong takeUntil method. This is more a variation on takeWhile:

http://reactivex.io/RxJava/javadoc/rx/Observable.html#takeUntil(rx.functions.Func1)

[dalewking]

Haven't tested it but I think this would be a working implementation.

public Stream<T> takeUntil(final Predicate<? super T> predicate) {
    return new Stream<T>(new LsaExtIterator<T>() {

        @Override
        protected void nextIteration() {
            hasNext = iterator.hasNext() && !(isInit && predicate.test(next));
            if(hasNext)
            {
                next = iterator.next();
            }
        }
    });
}

[dalewking]

So as an example:

IntStream.range(0, 10).takeUntil(x -> x > 3)

Would be a stream with 0, 1, 2, 3, 4

[aNNiMON]

@dalewking ok, this possible. Thanks!

[dalewking]

Refactored version:

public Stream<T> takeUntil(final Predicate<? super T> predicate) {
    return new Stream<T>(new LsaExtIterator<T>() {

        @Override
        protected void nextIteration() {
            hasNext = iterator.hasNext() && !(isInit && predicate.test(next));
            next = hasNext ? iterator.next() : null;
        }
    });
}

Setting next to null is so we don't keep a reference to the last item which we no longer need.

[dalewking]

Your fix does not release the reference to the last item emitted when it is no longer needed.

The null part of this:

next = hasNext ? iterator.next() : null;

[aNNiMON]

That's my fault. Thank you so much!