module W05_1
where

import Prelude hiding (splitAt)


-- Split a list into two at the element whose position is specified by the
-- first argument to the function
--
-- Examples: splitAt 0 [1,2,3,4,5] = ([],[1,2,3,4,5])
--           splitAt 3 [1,2,3,4,5] = ([1,2,3],[4,5])
--
splitAt :: Int -> [a] -> ([a],[a])
splitAt 0 xs     = ([], xs)
splitAt n (x:xs) = let
	             (ys, zs) = splitAt (n - 1) xs
	           in
	           (x:ys, zs)

-- Given a nested list (ie, list of lists) of integers, yield a list that
-- contains the largest element of each of the sublists (and zero for empty
-- sublists)
--
-- Example: largest [[1,2,3], [2,3,1], [4,0], []] = [3,3,4,0]
--
largest :: [[Int]] -> [Int]
largest []       = []
largest (xs:xss) = largerThan 0 xs : largest xss
		   where
		     largerThan k []     = k
		     largerThan k (x:xs)
		       | x > k     = largerThan x xs
		       | otherwise = largerThan k xs