CIS194 Homework3 Local Maxima

splitList :: [a] -> [[a]]
splitList [] = [[]]
splitList list = scanr (\elem new -> [elem] ++ new) [] list

selectFirst:: Int -> [[a]] -> [[a]]
selectFirst n [[]] = [[]]
selectFirst n list = map (take n) (filter (\l -> length l >= 3) list)

cmpElem::(a -> a -> Bool) -> a -> a -> a -> Bool
cmpElem f a b c = (f a b) && (f c b)

localMaxima :: [Integer] -> [Integer]
localMaxima l = let split_list = splitList l
                    three_elem_list = selectFirst 3 split_list
                    valid_elem_list = filter (\[a, b, c] -> cmpElem (<) a b c) three_elem_list
                in map (\[a, b, c] -> b) valid_elem_list