{-
- 1.
- Using a library function define halve :: [a] -> ([a], [a])
-}
halve   :: [a] -> ([a], [a])
halve xs = (take h xs, drop h xs)
	where
		n = length xs
		h = n `div` 2

{-
- 2.
- Define safetail with
- * conditional expression
- * guarded equation
- * pattern matching
-}

-- safetail with conditional
safetail   :: [a] -> [a]
safetail xs = if null xs then xs else tail xs

-- safetail with guarded equation
safetail'   :: [a] -> [a]
safetail' xs | null xs   = xs
             | otherwise = tail xs

-- safetail with pattern matching
safetail_   :: [a] -> [a]
safetail_ [] = []
safetail_ xs = tail xs