Proposal: containers: add indexing operations for Set

I'd like to add the following indexing operations for Data.Set.Set, to complement the existing functions for Data.Map.Map: findIndex :: Ord a => a -> Set a -> Int lookupIndex :: Ord a => a -> Set a -> Maybe Int elemAt :: Int -> Set a -> a deleteAt :: Int -> Set a -> Set a A tentative patch can be found here https://github.com/haskell/containers/pull/13 Discussion period: 2 weeks