haskell - cards shuffle

cards.hs

-- | Seeds a list of cards with a random value                    
seedCards :: StdGen -> [Card] -> [(Card, Int)]                    
seedCards g []     = []                                           
seedCards g (c:cs) = x:seedCards ng cs                            
   where (seed, ng) = randomR(1, 10000) g :: (Int, StdGen)        
         x          = (c, seed)                                   
                                                                  
-- | Makes an ordered deck of cards                               
makeDeck :: [Card]                                                
makeDeck = [Card v s | v <- [Ace .. King], s <- [Heart .. Spade]] 
                                                                  
-- | Makes a randomly shuffled deck of cards                      
makeShuffledDeck :: StdGen -> [Card]                              
makeShuffledDeck g = [x | c <- sorted, let x = fst c]             
   where cards  = seedCards g makeDeck                            
         sorted = sortBy (compare `on` snd) cards