Incrementing Subsequences

[nipafx]

I found one more operation in my notes, but I've only implemented that for fun and haven't used it in practice, so not sure how much sense it makes: It's about creating groups of variable length, where within each group the elements are in increasing order according to their natural order or a given comparator. E.g.:

Stream.of(1, 3, 5, 6, 2, 4)
	.gather(incrementing()) // Stream<List<Integer>>
	.forEach(System.out::println); // [1, 3, 5] [6] [2, 4]

Thanks to generics, it should be possible to make incrementing() (or whatever it ends up being called) non-applicable to a stream whose elements don't extend Comparable. The alternative incrementing(Comparator) would of course apply to all streams.

The symmetrical decrementing variant should probably be added together with this one.

[tginsberg]

Hi! These two (incrementing and decrementing) are on my list, along with nonIncrementing (so, [1,1,2,1] -> [1,1,2],[1]) and nonDecrementing. I think that covers the full set of possibilities here? You're right that I think this would only apply to streams of elements that implement Comparable, or I suppose a version could be made that takes a Comparator. At any rate, on the list! :)

Not sure how happy I am with the names "nonIncrementing/nonDecrementing" even if they do describe what's happening. I'll take a walk and think about the name.

Thanks again @nipafx!

[tginsberg]

Hey @nipafx - I put in a PR which is my take on this. I did have one question about your example:

Stream.of(1, 3, 5, 6, 2, 4)
	.gather(incrementing()) // Stream<List<Integer>>
	.forEach(System.out::println); // [1, 3, 5] [6] [2, 4]

I think the result should be [1, 3, 5, 6] [2, 4], yes?

[nipafx]

Oh, yes. 🙈 I wanted to show that a group may consist of just one element, but got the numbers wrong.

[tginsberg]

Merged something I'm happy with. I realize this is not fully documented in README, but I have plans to fully document each operation in an adoc-powered website so I'll save the work for that. :)