data Values = Two | Three | Four | Five | Six | Seven | Eight | Nine | Ten | Jack | Queen | King | Ace deriving (Show)

data Suits = Spades | Hearts | Diamonds | Clubs deriving (Show)

type Cards = (Suits, Values)
{- greaterCard

   Compares the values of two playing cards and establishes which has the greatest value
   PRE: Values = [2, ..., 14]
   RETURNS: Card with the greatest value
   EXAMPLES: greaterCard (Spades Ace) (Spades King) = True
             greaterCard (Hearts King) (Spades King) = False
   -}

greaterCard :: Cards -> Cards -> Bool
greaterCard (suits1, value1) (suits2, value2)
      | convertValue value1 > convertValue value2 = True
      | convertValue value1 == convertValue value2 = if convertSuits suits1 > convertSuits suits2 then True else False
      | otherwise = False

{- convertValue

  -}
convertValue :: Values -> Int
convertValue Two = 2
convertValue Three = 3
convertValue Four = 4
convertValue Five = 5
convertValue Six = 6
convertValue Seven = 7
convertValue Eight = 8
convertValue Nine = 9
convertValue Ten = 10
convertValue Jack = 11
convertValue Queen = 12
convertValue King = 13
convertValue Ace = 14

{- convertSuits

  -}
convertSuits :: Suits -> Int
convertSuits Spades = 4
convertSuits Hearts = 3
convertSuits Diamonds = 2
convertSuits Clubs = 1

(+?) :: Maybe Int -> Maybe Int -> Maybe Int
_ +? Nothing = Nothing
Nothing +? _ = Nothing
Just x +? Just y = Just (x+y)

(-?) :: Maybe Int -> Maybe Int -> Maybe Int
_ -? Nothing = Nothing
Nothing -? _ = Nothing
Just x -? Just y = Just (x-y)

(*?) :: Maybe Int -> Maybe Int -> Maybe Int
_ *? Nothing = Nothing
Nothing *? _ = Nothing
Just x *? Just y = Just (x * y)

(/?) :: Maybe Int -> Maybe Int -> Maybe Int
_ /? Nothing = Nothing
Nothing /? _ = Nothing
Just x /? Just y
    | y == 0 = Nothing
    | otherwise Just (div x y)