Add support for unbounded ranges

[lukaseder]

The org.jooq.lambda.tuple.Range type currently supports only bounded ranges. It would be nice to support also unbounded ranges, where null corresponds to "infinity".

For example:

// From 1 to infinity
new Range(1, null);

// From -infinity to 1
new Range(null, 1);

[tlinkowski]

Just for reference (in case you wanted to further improve your ranges), Guava has quite advanced range support (including e.g. open/closed bounds).

[Artus2b]

@tlinkowski Indeed I found the Guava and Apache Common Ranges implementations, while I was writing the algorithm of overlaps(Range a, Range b) which was a bit cumbersome.
Are you saying those libs nullify the usefulness of the issue? Or that we should use Guava's implementation in the proposed fix?

Edit: in any case here's my PR #351 :) I'd be happy to know what you think.

[tlinkowski]

Are you saying those libs nullify the usefulness of the issue? Or that we should use Guava's implementation in the proposed fix?

@Artus2b I don't know which is best here. In your PR, you mentioned how it works in PostgreSQL, so aligning to its Range Types (independently of other libs) in certainly one option.

To sum up, I'm just saying it's good to be aware of other solutions (thx for mentioning Apache Commons - forgot about that) so that an informed decision can be made.

[lukaseder]

Are you saying those libs nullify the usefulness of the issue?

Everything jOOλ does is available in one way or another through a different means. After all, we're all working with turing complete languages, so everything is possible, including NIH, home grown solutions to every single problem :)

Given that we already have a Range type, it's definitely worth exploring what else it can offer, and I do like this idea, regardless of what Guava does.

[lukaseder]

I think that all changes from your PR are now addressed:

• Documentation of inclusivity of current range implementation
• (Partially) Unbounded ranges
• Range.contains()

Thanks again for your suggestion and PR.