pull 'Set'-producing operations | & ~ up to 'Collection'

I was longing for Set operators/operations in Range instances. Namely union, intersection but why not also complement and exclusiveUnion.

Sure, I can do set(3..5).union(set(4..6)), but is there any reason that Range couldn’t satisfy Set? I read through #3557 and the current interfaces and their implementations and although I didn’t perhaps catch everything, I felt I should ask.

Since all operations except intersection may result in split ranges, the implied return value of Set is actually just fine. One could of course have a more specific Range<Element> intersectionWithRange(Range<Element> other) for convenience.

For these set operations one would naturally not care if the ranges are increasing or decreasing - the result would be the same i.e. the result would be normalized.

As for an actual implementation it would perhaps be beneficial to override the default implementations from the Set interface for more efficient operation (as long as the “other” set is of same type as “this” set), but they would still be “just Sets”…

Thanks for listening…

[gavinking]

I’ve implemented this idea (it was really straightforward) and it seems to be working well. I’ll push it to a branch later.

[gavinking]

One possible reasonable thing to do would be to define | and & for the Collection interface, but have them always produce Sets. That is, simply pull the current union() and intersection() methods up to Collection from Set.

That would be a change with pretty minimal impact on the language, that makes the existing | and & operators much more useful.

For example, [1->"hello", 3->"world"] | map { 1->"goodbye", 2->"sweet" } would be equal to set { 1->"hello", 3->"world", 1->"goodbye", 2->"sweet" }.