ParseCard.hs

data Suit = Spades | Hearts | Clubs | Diamonds
  deriving Show

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

data Card = Card
  { rank :: Rank
  , suit :: Suit
  } deriving Show

parseCard :: String -> Maybe Card
parseCard (r:s:[]) = do
  r <- rankFrom r
  s <- suitFrom s
  pure $ Card r s
parseCard _ = Nothing

rankFrom :: Char -> Maybe Rank
rankFrom 'A' = Just Ace
rankFrom '2' = Just Two
-- ...
rankFrom 'K' = Just King
rankFrom  _  = Nothing

suitFrom :: Char -> Maybe Suit
suitFrom 'S' = Just Spades
suitFrom 'H' = Just Hearts
suitFrom 'C' = Just Clubs
suitFrom 'D' = Just Diamonds
suitFrom  _  = Nothing