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 <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'.
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