mySum :: Num a => [a]->a
mySum lst
    | null lst          = 0
    | otherwise         = head lst + mySum (tail lst)

mySum' :: Num a => [a]->a
mySum' [] = 0
mySum' (h:t) = h + mySum' t

myMaximum :: Ord a => [a]->a
myMaximum [] = error "Maximum of empty list"
myMaximum [x] = x
myMaximum (h:t)
    | h >= m     = h
    | otherwise  = m
    where m = myMaximum t

-- Polynomial coeff. in descending order
polDerivative :: Num a => [a]->[a]
polDerivative [] = []
polDerivative [a] = []
polDerivative (h:t) =
    (fromIntegral(length t) * h) : polDerivative t 

-- Polynomial coeff. in descending order
polAntiderivative :: (Num a, Fractional a) => [a]->[a]
polAntiderivative [] = [0]
polAntiderivative (h:t) =
    (h / (fromIntegral(length t) + 1)):polAntiderivative t