RosettaCodeData/Task/Damm-algorithm/Haskell/damm-algorithm.hs

22 lines
685 B
Haskell

import Data.Char (digitToInt)
import Text.Printf (printf)
damm :: String -> Bool
damm = (==0) . foldl (\r -> (table !! r !!) . digitToInt) 0
where
table =
[ [0, 3, 1, 7, 5, 9, 8, 6, 4, 2]
, [7, 0, 9, 2, 1, 5, 4, 8, 6, 3]
, [4, 2, 0, 6, 8, 7, 1, 3, 5, 9]
, [1, 7, 5, 0, 9, 8, 3, 4, 2, 6]
, [6, 1, 2, 3, 0, 4, 5, 9, 7, 8]
, [3, 6, 7, 4, 2, 0, 9, 5, 8, 1]
, [5, 8, 6, 9, 7, 2, 0, 1, 3, 4]
, [8, 9, 4, 5, 3, 6, 2, 0, 1, 7]
, [9, 4, 3, 8, 6, 1, 7, 2, 0, 5]
, [2, 5, 8, 1, 4, 3, 6, 7, 9, 0] ]
main :: IO ()
main = mapM_ (uncurry(printf "%6s is valid: %s\n") . ((,) <*> show . damm) . show)
[5724, 5727, 112946, 112949]