On Jun 22, 6:46 am, Bulat Ziganshin <bulat.zigans...@gmail.com> wrote:
> Hello Kamil,
>
> Monday, June 22, 2009, 12:01:40 AM, you wrote:
>
> > Right... Python uses hashtables while here I have a tree with log n
>
> you can try this pure hashtable approach:
>
> import Prelude hiding (lookup)
> import qualified Data.HashTable
> import Data.Array
> import qualified Data.List as List
>
> 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)
>
> main = do let assoclist = [("one", 1), ("two", 2), ("three", 3)]
> hash = create 10 (fromEnum . Data.HashTable.hashString)
> assoclist
> print (lookup "one" hash)
> print (lookup "zero" hash)
It does not compile:
No instance for (Num (String, b))
arising from the literal `3' at foo.hs:23:61
Possible fix: add an instance declaration for (Num (String, b))
In the expression: 3
In the expression: ("three", 3)
In the expression: [("one", 1), ("two", 2), ("three", 3)]
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