import SimplePrelude hiding (last, unzip, lines, take)

-- Compute the last element of a list:
last :: [a] -> a
last [x]          = x
last (x:xs@(_:_)) = last xs


-- Split a list of pairs into the lists of the components:
unzip :: [(a,b)] -> ([a], [b])
unzip []            = ([], [])
--unzip ((x,y) : xys) = let (xs,ys) = unzip xys
--                      in (x:xs, y:ys)
unzip ((x,y) : xys) = (x:xs, y:ys)
 where (xs,ys) = unzip xys

-- Breaks a string into a list of lines, where each line is terminated
-- with a newline \n character and does not contain newline characters
lines :: String -> [String]
lines ""        = []
lines ('\n':cs) = "" : lines cs
lines (c : cs)  = case lines cs of
                    []     -> [ [c] ]
                    (l:ls) -> (c : l) : ls

-- Factorial function:
fac :: Int -> Int
fac n | n == 0    = 1
      | otherwise = n * fac (n - 1)


-- Returns prefix of maximal length n of a list.
take :: Int -> [a] -> [a]
take n xs | n <= 0    = []
          | otherwise = case xs of []     -> []
                                   (x:xs) -> x : take (n - 1) xs