bulat.ziganshin:
> Hello Don,
>
> Wednesday, November 12, 2008, 12:51:33 AM, you wrote:
>
> >> btw, i made here some time ago proposal about pure hashtables
>
> > Did you end up implementing this?
>
> yes, i have published here all the 10 lines of implementation :)))
>
> citing letter to you:
>
> actually, writing HT module from scratch is
> very easy - all we need is a prime searching function (in order to
> establish array size). everything else:
>
> data HT a b = HT (a->Int) (Array Int [(a,b)])
>
> -- size is the size of array (we implent closed hash)
> -- hash is the hash function (a->Int)
> -- list is assoclist of items to put in hash
> create size hash list = HT hashfunc
> (accumArray (flip (:))
> []
> (0, arrsize-1)
> (map (\(a,b) -> (hashfunc a,b)) list)
> )
>
> where arrsize = head$ filter (>size)$ iterate (\x->3*x+1) 1
> hashfunc a = hash a `mod` arrsize
>
>
> lookup a (HT hash arr) = List.lookup a (arr!hash a)
>
>
> example:
>
> main = do let assoclist = [("one", 1), ("two", 2), ("three", 3)]
> hash = HT.create 10 Data.HashTable.hashString assoclist
> print (HT.lookup "one" hash)
> print (HT.lookup "zero" hash)
>
>
If this structure is useful, you should release it on Hackage.
You've not tested the performance though, I imagine, versus
say, hasing into an IntMap?
-- Don
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