SumTwoFoldl.hs

sumTwoFoldl :: [Int] -> [Int] -> [Int]
sumTwoFoldl x y =
    let (sum, carry)                = foldl accum ([], 0) $ zip x y
        accum (total, carry) (x, y) =
            let t = x + y + carry
                (n, nc) =
                    if t > 9
                        then (t - 10, 1)
                        else (t, 0)
            in (n : total, nc)
        final                       =
            if carry > 0
                then carry : sum
                else sum
    in reverse final