Trello hash haskell

gistfile1.hs

-- the "hash" is actually a number in base 37, starting at 7
-- and digits are less than 15

data Letter = A | C | D | E | G | I | L | M | N | O | P | R | S | T | U | W deriving (Eq, Ord, Bounded, Enum, Show, Read)

-- point free and obfuscated version for demo purpose
reverseHash :: Int -> [Letter]
reverseHash = tail . reverse . map (toEnum . (`mod` 37)) . takeWhile (/= 0) . iterate (`div` 37)

main :: IO ()
main = do
  let target = 956446786872726
  let decomposition = takeWhile (/= 0) . iterate (`div` 37) $ target
  let result = map (toEnum . (`mod` 37)) decomposition :: [Letter]
  -- tail is here to remove the first digit which is 7 (the initial value)
  let finalResult = tail $ reverse result
  putStrLn $ "Result is " ++ (concat $ map show finalResult)
  putStrLn $ "Result with point free version (should be the same): " ++ (concat $ map show $ reverseHash target)