How to generalize code?

Question

I am learning haskell and write for exercise following function:

  cipherCeasar :: Char -> Int -> Char
  cipherCeasar c i
    | isUpper c = chr (isBiggerMax ((+) i $ ord c) (ord 'A') (ord 'Z'))                    
    | otherwise = chr (isBiggerMax ((+) i $ ord c) (ord 'a') (ord 'z'))

As you can see the two lines of codes after guard are almost the same.
How can I generalize code or it is ok so?

Answer 1

You can use a helper function:

cipherCeasar :: Char -> Int -> Char
cipherCeasar c i
  | isUpper c = cipherBetween 'A' 'Z'
  | otherwise = cipherBetween 'a' 'z'
  where cipherBetween min max = chr (isBiggerMax ((+) i $ ord c) (ord min) (ord max))