Improve code in Haskell solution for Problem 54

Haskell/p054.hs

@@ -46,14 +46,15 @@
 
 import Data.List
 import Data.Function
+import Data.Maybe
 import System.IO
 
 data Value = Two | Three | Four | Five | Six | Seven | Eight | Nine | Ten | Jack | Queen | King | Ace
-             deriving (Eq, Ord, Show, Read, Bounded, Enum)
+             deriving (Eq, Ord, Show, Bounded, Enum)
 data Suit = Hearts | Diamonds | Clubs | Spades deriving (Eq, Show)
 
-data Card = Card { value :: Value
-                 , suit :: Suit
+data Card = Card { value :: Maybe Value
+                 , suit :: Maybe Suit
                  } deriving (Eq, Show)
 
 instance Ord Card where
@@ -65,26 +66,28 @@ data PokerGame = PokerGame { player1 :: Hand
                            , player2 :: Hand
                            } deriving (Eq, Show)
 
-getValue :: Char -> Value
-getValue '2' = Two
-getValue '3' = Three
-getValue '4' = Four
-getValue '5' = Five
-getValue '6' = Six
-getValue '7' = Seven
-getValue '8' = Eight
-getValue '9' = Nine
-getValue 'T' = Ten
-getValue 'J' = Jack
-getValue 'Q' = Queen
-getValue 'K' = King
-getValue 'A' = Ace
+getValue :: Char -> Maybe Value
+getValue '2' = Just Two
+getValue '3' = Just Three
+getValue '4' = Just Four
+getValue '5' = Just Five
+getValue '6' = Just Six
+getValue '7' = Just Seven
+getValue '8' = Just Eight
+getValue '9' = Just Nine
+getValue 'T' = Just Ten
+getValue 'J' = Just Jack
+getValue 'Q' = Just Queen
+getValue 'K' = Just King
+getValue 'A' = Just Ace
+getValue _ = Nothing
 
-getSuit :: Char -> Suit
-getSuit 'H' = Hearts
-getSuit 'D' = Diamonds
-getSuit 'C' = Clubs
-getSuit 'S' = Spades
+getSuit :: Char -> Maybe Suit
+getSuit 'H' = Just Hearts
+getSuit 'D' = Just Diamonds
+getSuit 'C' = Just Clubs
+getSuit 'S' = Just Spades
+getSuit _ = Nothing
 
 readCard :: String -> Card
 readCard (v:s:_) = Card{value=getValue v,suit=getSuit s}
@@ -95,14 +98,14 @@ readGame g = PokerGame{player1=map readCard (take 5 (words g)), player2=map read
 royalFlush :: Hand -> Bool
 royalFlush h =
     let hs = sort h
-    in length (head (groupBy ((==) `on` suit) hs)) == 5 && [Ten .. Ace] == map value hs
+    in length (head (groupBy ((==) `on` suit) hs)) == 5 && [Ten .. Ace] == map (fromJust . value) hs
 
 straightFlush :: Hand -> Bool
 straightFlush h = 
     let hs@(x:_) = sort h
-        start = value x
+        start = fromJust . value $ x
     in length (head (groupBy ((==) `on` suit) hs)) == 5 &&
-        take 5 [start..] == map value hs
+        take 5 [start..] == map (fromJust . value) hs
 
 fourOfAKind :: Hand -> Bool
 fourOfAKind h =
@@ -121,8 +124,8 @@ flush h =
 straight :: Hand -> Bool
 straight h =
      let hs@(x:_) = sort h
-         start = value x
-     in take 5 [start..] == map value hs
+         start = fromJust . value $ x
+     in take 5 [start..] == map (fromJust . value) hs
 
 three :: Hand -> Bool
 three h =