-- using conditionals
safetail :: [a] -> [a]
safetail a = if null a then [] else tail a

-- using guarded equations
safetail'   :: [a] -> [a]
safetail' xs | null xs    = []
	         | otherwise = tail xs

-- using pattern matching
safetail''       :: [a] -> [a]
safetail''    []  = []
safetail'' (_:xs) = xs

-- my or operator
(||!)          :: Bool -> Bool -> Bool
True  ||! True  = True
True  ||! False = True
False ||! True  = True
False ||! False = False

-- another or operator
(||#)          :: Bool -> Bool -> Bool
False ||# False = False
_     ||# _     = True

-- and another or operator
(||@)      :: Bool -> Bool -> Bool
False ||@ b = b
True  ||@ _ = True