Re: PROPOSAL: Add `disjoint` method to `Data.IntSet`

I am thinking along the lines of Tikhon. Sets "overlap" is a rather uncommon term. [If we were all constructivists, the situation would be different. Constructively, "overlap" is certainly the primitive notion, and "disjoint" only its negation.] We can't introduce a positive term for everything. For instance, we all use not . null rather than having predicates like "isCons", "inhabited" etc. On 19.12.2017 19:01, Tikhon Jelvis wrote:

In practice, I hear people talking about "disjoint" sets all the time—it comes up a lot more often than "overlapping" or "not overlapping". It might have a negative in the name semantically, but it's used as an atomic word in practice. (That is, when people say "disjoint" they're *thinking* "disjoint" as opposed to "not joint" or "not overlapping".)

I'm in favor of naming functions with common usage in mind, and I think "disjoint" is the word people use most often in this context.

On Tue, Dec 19, 2017 at 7:44 AM, Henning Thielemann mailto:lemming@henning-thielemann.de> wrote:

On Tue, 19 Dec 2017, Víctor López Juan wrote:

I'm thinking that `disjoint` is already a negation: (dis- (not) + joint (united)). When composing with `not`, the user gets a double negation `not (disjoint x y)`. There is a then a small mental effort required to go from "not disjoint" to "overlapping".

If we are going to have only one of the two properties, I would rather have the positive one (`overlaps`) as primitive. Then `disjoint` would be written "not (overlaps x y)", which reads quite easily. (Or even "not (x `overlaps` y)").

I also dislike double negation and think that 'disjoint' is one. I'd prefer to see both 'overlap' and 'disjoint'. _______________________________________________ Libraries mailing list Libraries@haskell.org mailto:Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

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