On Jun 22, 6:46 am, Bulat Ziganshin
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)]