<div dir="ltr"><div dir="auto">Would all constructivists actually say so? I'd think there could be some who think that<div dir="auto"><br></div><div dir="auto">disjoint :: (s, t : Set a) -> x : a -> Either (Not (elem x s)) (Not (elem x t))</div><div dir="auto"><br></div><div>in which case being disjoint is a stronger property than just not overlapping. But of course,<br></div><div>none of this is really relevant to Haskell.<br></div><div dir="auto"><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Dec 19, 2017 6:46 PM, "Andreas Abel" <<a href="mailto:abela@chalmers.se" target="_blank">abela@chalmers.se</a>> wrote:<br type="attribution"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I am thinking along the lines of Tikhon.<br>
<br>
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.]<br>
<br>
We can't introduce a positive term for everything. For instance, we all use<br>
<br>
not . null<br>
<br>
rather than having predicates like "isCons", "inhabited" etc.<br>
<br>
On 19.12.2017 19:01, Tikhon Jelvis wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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".)<br>
<br>
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.<br>
<br>
On Tue, Dec 19, 2017 at 7:44 AM, Henning Thielemann <<a href="mailto:lemming@henning-thielemann.de" target="_blank">lemming@henning-thielemann.de</a> <mailto:<a href="mailto:lemming@henning-thielemann.de" target="_blank">lemming@henning-thiele<wbr>mann.de</a>>> wrote:<br>
<br>
<br>
On Tue, 19 Dec 2017, Víctor López Juan wrote:<br>
<br>
I'm thinking that `disjoint` is already a negation:<br>
(dis- (not) + joint (united)). When composing with `not`, the<br>
user gets<br>
a double negation `not (disjoint x y)`. There is a then a small<br>
mental<br>
effort required to go from "not disjoint" to "overlapping".<br>
<br>
If we are going to have only one of the two properties, I would<br>
rather<br>
have the positive one (`overlaps`) as primitive. Then `disjoint`<br>
would<br>
be written "not (overlaps x y)", which reads quite easily.<br>
(Or even "not (x `overlaps` y)").<br>
<br>
<br>
I also dislike double negation and think that 'disjoint' is one. I'd<br>
prefer to see both 'overlap' and 'disjoint'.<br>
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Andreas Abel <>< Du bist der geliebte Mensch.<br>
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