在haskell中减去教堂数字

factorial :: Int -> Int
factorial 0 = 1
factorial n = n * factorial (n - 1)

churchNumeral :: Int -> Int
churchNumeral n = sum [factorial i | i <- [1..n]]

main :: IO ()
main = do
  let n = 10
  putStrLn $ "The " ++ show n ++ "th church numeral is: " ++ show (churchNumeral n)

subtractChurchNumerals :: Int -> Int -> Int
subtractChurchNumerals x y = churchNumeral x - churchNumeral y

main :: IO ()
main = do
  let x = 10
  let y = 5
  putStrLn $ "The difference between the " ++ show x ++ "th and " ++ show y ++ "th church numerals is: " ++ show (subtractChurchNumerals x y)