检查字符串是否在“i”字母处是回文？

Question

I got a program that checks if string is palindrome or not. I want to add functionality that lets user check if given string is palindrome at i letters. For example if string is "abbaabba" and user gives number 4 it returns true because "abba" is palindrome. If user gives 5 then it returns false, because "abbaa" is not palindrome.

This is what I've done so far

palindromes:: String -> Int -> Bool

palindromes p i
   | p == reverse p = True
   | otherwise = False

How do I add that functionality?

Answer 1

You can make use of take :: Int -> [a] -> [a] here to pre-process the string:

palindromes :: Eq a => [a] -> Int -> Bool
palindromes p i = p' == reverse p'
    where p' =