>>23
import Control.Monad

isSorted :: Ord a => [a] -> Either Int Ordering
isSorted [] = Right EQ
isSorted [_] = Right EQ
isSorted xs = foldM f EQ $ zip [1..] $ zipWith compare xs $ tail xs
　　where
　　　f EQ (_,x) = Right x
　　　f acc (_,EQ) = Right acc
　　　f acc (i,x)
　　　　　| acc == x = Right acc
　　　　　| otherwise = Left i

main :: IO ()
main = do
　　test [6,6,3,2,6,4,7,4,7,4] -- => 4
　　test [2,3,4,4,4,6,6,6,7,7] -- => AS
　　test [7,7,6,6,6,4,4,4,3,2] -- => DES
　　test [1,1,1,1,1,1,1,1,1,1] -- => EQ
　　test ([] :: [Int]) -- => EQ
　　test [1] -- => EQ

test :: (Ord a, Show a) => [a] -> IO ()
test xs = do
　　putStr $ show xs ++ " => "
　　putStrLn $ case isSorted xs of
　　　　Left i -> show i
　　　　Right EQ -> "EQ"
　　　　Right LT -> "AS"
　　　　Right GT -> "DES"