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)"). — Víctor Den 2017-12-19 kl. 16:01, skrev Joachim Breitner:

Hi,

Am Dienstag, den 19.12.2017, 13:44 +0100 schrieb Andreas Abel:

...

+1 for "disjoint".

+1

...

I think "overlaps" falls below the Fairbairn threshold.

✓

...

I always wondered why there is a "notMember" function in the Set interface, saving us 3 key presses.

Probably because of use like this:

filter (`notMember` seen) todo -- pretty

vs.

filter (not . (`member` seen)) todo -- too many parenthesis.

Of course

filter (\x -> not (x `member` seen)) todo -- is also ok

And I will refrain from pointing out that with the idea of no-white- space-means-higher-precedence[1] would allow

filter (not . `member`seen) todo -- too many parenthesis.

[1] https://www.joachim-breitner.de/blog/730-Less_parentheses

...

One thing to consider: Data.Set should then also be equipped with a function "disjoint", to keep interfaces in sync.

✓

Cheers, Joachim

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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'. _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

Would all constructivists actually say so? I'd think there could be some who think that disjoint :: (s, t : Set a) -> x : a -> Either (Not (elem x s)) (Not (elem x t)) in which case being disjoint is a stronger property than just not overlapping. But of course, none of this is really relevant to Haskell. On Dec 19, 2017 6:46 PM, "Andreas Abel" wrote:

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 < lemming@henning-thielemann.de 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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-- Andreas Abel <>< Du bist der geliebte Mensch.

Department of Computer Science and Engineering Chalmers and Gothenburg University, Sweden

andreas.abel@gu.se http://www.cse.chalmers.se/~abela/ _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries