https://www.reddit.com/r/dailyprogrammer/comments/3h9pde/20150817_challenge_228_easy_letters_in/

are-letters-sorted.hs

input :: [String]
input = [
  "billowy",
  "biopsy",
  "chinos",
  "defaced",
  "chintz",
  "sponged",
  "bijoux",
  "abhors",
  "fiddle",
  "begins",
  "chimps",
  "wronged"]

isSorted :: (a -> a -> Bool) -> [a] -> Bool
isSorted cmp xs = and $ zipWith cmp xs (tail xs)

solve :: String -> String
solve xs
  | isSorted asc xs  = xs ++ " IN ORDER"
  | isSorted desc xs = xs ++ " REVERSE ORDER"
  | otherwise        = xs ++ " NOT IN ORDER"
  where asc = (<=)
        desc = (>=)

main :: IO ()
main = mapM_ (putStrLn . solve) input