How to use sets in D?

[mark]

On Sunday, 8 March 2020 at 17:58:16 UTC, Jesse Phillips wrote:
> On Friday, 7 February 2020 at 19:37:08 UTC, mark wrote:
[snip]
> I think I've usually used the associative arrays, but I also 
> think I tend to avoid using this approach but couldn't quite 
> remember what I do instead.
>
> I believe I have started just using an array.
>
> arr ~= addMyData;
> arr.sort.uniq
>
> Then I make use of the algorithms here.
>
> https://dlang.org/phobos/std_algorithm_setops.html

I can see the sense in that for use with union & intersection.
However, AA's (assuming they are hashes under the hood) give O(1) 
for `in` whereas those algorithms like the rbtree are O(lg n) for 
`in`, and most of what I'm doing at the moment is `in`. I'll keep 
the idea in mind though, because I have use cases for 
intersection.