Question

So I write a function with the definition

getLastDigits :: String -> String

which finds repeating digits on the end of a String

So, for example.

getLastDigits "1000" should give "000"
getLastDigits "19990299" should give "99"

Coming from a java background I’m not quite sure how to structure this program. I’m thinking of using foldr but I’m fairly sure I can’t stop the fold half way when the repeating digits end.

-edit solved. Use the group function.

Answer 1

Okay then, if it is not homework:

lastDigits :: String -> String
lastDigits s = firstDigits . reverse $ s
  where firstDigits :: String -> String
        firstDigits (x:xs) = x : takeWhile (== x) xs
        firstDigits [] = []