Re: [Haskell-cafe] Re: A typeclass for Data.Map etc?

On Fri, Feb 20, 2009 at 6:40 AM, Achim Schneider wrote:

wren ng thornton wrote:

...

(b) allows instances to have a fixed type for keys (like Data.Trie and Data.IntMap have),

Can't we do some type magic to automagically select Data.Trie if the key is a (strict) bytestring?

I believe this is a key feature of Associated Types: you can create "self-optimizing libraries" that select a different container structure depending on the type. For example, class XMapK k where type XMap k :: * -> * insert :: k -> XMap k v -> XMap k v and then instance XMapK Int where type XMap Int = Data.IntMap.IntMap insert = Data.IntMap.insert etc. Alex