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

[Mark Wotton]

On Thu, Feb 19, 2009 at 9:51 PM, Eugene Kirpichov <ekirpichov at gmail.com> wrote:
> Greetings,
>
> Is there a typeclass for mappings with a Data.Map-like interface, with
> stuff like: empty, insert, insertWithKey, unionWith etc. ?
> And, probably, a similar typeclass for mutable mappings like Data.Hashtable.
>
> Looks like such a thing would be useful; as for now, I see at least
> two applications: Data.Map and Data.Trie (bytestring-trie) - it's a
> pity that they have rather similar interfaces, but the latter lacks
> many methods and some are named in a different way. Also, Data.Map has
> some inconsistensies, too: for instance, it has an insertWith' but
> lacks a unionWith'. "One typeclass for all" would eliminate these
> inconsistencies.
>
> I'm asking mainly because I've been wondering why noone has yet
> written a mutable hashtable package with a MArray-like interface, I
> wrote a small thing myself and I am unsure as to what interface it
> should have.

Probably not adding anything terribly useful to this except to say
that it'd be useful to me too - I've written a binding to a perfect
hashing library (PerfectHash on hackage) which implements only
'fromList' and 'lookup', so a slightly more fine-grained type class
hierarchy would be nice. (This particular implementation is useful
when you have a lot of keys, but all known at run-time.)

Mark

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