Add a Set type matching the std HashSet API

[Josh Stone]

Just like in std, it can start with the simple definition wrapping a map:

pub struct FlurryHashSet<T, S = RandomState> {
    map: FlurryHashMap<T, (), S>,
}

[Jon Gjengset]

The Java code's KeySetView may also be of interest.

[Jon Gjengset]

We now have a basic HashSet type, but it'd be great to get something along the lines of HashMapRef for HashSet too!

[Gark Garcia]

We now have a basic HashSet type, but it'd be great to get something along the lines of HashMapRef for HashSet too!

Is that a case of simply wrapping HashMapRef<T, ()> in a newtype? I could work on that if that's the case.

[Odin]

I think you'd want to wrap HashSet with HashSetRef similar to how HashMap is wrapped by HashMapRef.

[Gark Garcia]

I think you'd want to wrap HashSet with HashSetRef similar to how HashMap is wrapped by HashMapRef.

That's interesting. I'm not quite sure which way would be the most efficient memory wise. @jonhoo @cuviper opinions?

[Gark Garcia]

We'd be wrapping a wrapper either way...
I think wrapping HashMap<T, ()> directly should make the type's layout flatter, but I'm not sure.

[Jon Gjengset]

Ah, no, I was imagining we just do the same trick with HashSetRef as with HashMapRef, not that we wrap HashMapRef to make HashSetRef!

[Gark Garcia]

Ah, no, I was imagining we just do the same trick with HashSetRef as with HashMapRef, not that we wrap HashMapRef to make HashSetRef!

Makes sense.

[Gark Garcia]

@jonhoo What about the wrapping HashMap<T, ()> directly proposal?

[Jon Gjengset]

I think we should wrap HashSet, because HashSet actually has different methods than HashMap, and having the wrapper also do the translation from set-like methods to map-like methods (which HashSet is already doing) seems like unfortunate duplication.

[Jon Gjengset]

Closed by #78!