gistfile1.hs

sumUpTo :: Int -> [(Int, Int)]
sumUpTo n = map (\x -> (x, n - x)) [0..n]

mult xs ys = do
	cs <- map sumUpTo [0..maxCoef]
	return (sum $ map g $ filter f cs)
	where
		maxCoef = length xs + length ys - 2
		f (x, y) = x < length xs && y < length ys
		g (x, y) = (xs !! x) * (ys !! y)