Blogger - HTIF - intersection

-- |Finds lists intersection. O(2nlogn + 2n)
intersection :: Ord a => [a] -> [a] -> [a]
intersection = iter intersectF

intersectF :: Eq a => (Maybe a, Maybe a) -> [a] -> [a]
intersectF (Just x, Just y) acc = if x == y then x:acc else acc
intersectF _ acc = acc