Re: Symmetric difference for Set and IntSet

Map merges can do even more, because they work with arbitrary Applicative functors. So a functor like data Triple a = Triple a a a instance Applicative Triple where pure a = Triple a a a liftA2 f (Triple x y z) (Triple p q r) = Triple (f x p) (f y q) (f z r) can be used to calculate union, intersection, *and* symmetric difference all in one go. I should just bite the bullet and implement that for sets. On Fri, Jun 26, 2020, 1:16 PM Andrew Lelechenko wrote:

On 18 Jun 2020, at 23:42, Bardur Arantsson wrote:

...

I think it's probably going to be useful, but I would suggest an algorithm which actually returns each of the terms here (as a tuple), i.e.

The "added" bits The "removed" bits The "common" bits

This may not be *that* useful for sets per se, but I've lost count of how often I've had to implement a similar thing for maps.

This is probably orthogonal to my proposal here, because it does not improve the performance of symmetricDifference. Maps are more flexible in this aspect, because there are merge tactics, which allow to encode any set operation.

Best regards, Andrew _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries