Add 'IntSet'

[chshersh]

Currently there's only IntMap data structure. But it would be good to have IntSet as well.

This can be implemented easily by creating simple wrapper around IntMap like it's done here for AVL tree:

https://github.com/jfdm/idris-containers/blob/master/Data/AVL/Set.idr

All functions for IntMap should be duplicated:

• size
• member
• insert
• delete

If some functions from #5 will be implemented earlier than IntSet then those functions should be duplicated as well if possible.

[arbuztw]

Hi! I would like to work on this.
However, I am not sure how should I do on Functor and Foldable parts. Also, it seems that values function cannot be implemented directly as a wrapper, since there is no function returning the keys of a map. Does I need to add another function such like keys for IntMap?

[chshersh]

Hello, @arbuztw ! Please, take my apologies for not answering fast. I really happy that you're interested in contributing to this project :)

However, I am not sure how should I do on Functor and Foldable parts

Haskell version of IntSet doesn't have Functor and Foldable instances. And you can't implement these instances for IntSet so just don't do it :)

Does I need to add another function such like keys for IntMap?

As you correctly said, there's no keys functions for IntMap because it's not so trivial to implement. Thus you also shouldn't implement this function for IntSet.