Hello, The exercises of CIS 194 are really hard. Now I have to sum all the numbers in a array with a catch If a number is greater then 10 it has to be dived in single numbers. so [ 1 , 12, 3] will be [ 1, 1,2,3] and then sum up. So far I have this : -- | sum all the digits of a array sumDigits :: [Integer] -> Integer sumDigits n | n == 0 = acc | n < 10 = acc + n | otherwise = sumDigits acc + n `mod` 10 + n `rem` 10 But now I see a message that acc is not known which is not wierd. But when I do sumDigits n acc I see a message that sumDigits has only 1 parameter where I give it to, When I only had to sum up i is easy , I could use map [+] xs Anyone who can give a me tip without giving the answer otherwise I do not learn anything. Roelof