8. Warmups

These functions are just warmups to be used the first day you learn about data types. We presented solutions to 1 and 3. The fourth wasn’t visible until the first three were done.

1. (WhoseTurn)

   1. Create a WhoseTurn data type that could be Nobody, Player_A or Player_B.
   2. Write a nextPlayer function that says that after Player A comes Player B, and after Player B comes Player A. If it is nobody’s turn, then the next player is still nobody.

2. (Rock, Paper, Scissors)

   1. Create a RPS data type that holds the value Rock, Paper, or Scissors.

   2. Write the beats function.

      beats :: RPS -> RPS -> Bool
      beats _ _ = False
      
      check_beats = [Scissors `beats` Paper,
                     Rock `beats` Scissors,
                     Paper `beats` Rock,
                     not (Scissors `beats` Rock)]
      

3. (Wallet)

   1. A Wallet holds a number of fives ($5 bills) and ones ($1 bills). Create a data type so that both of the following represent a wallet with 8 five dollar bills and 3 one dollar bills.

      a = Wallet 8 3
      b = Wallet {fives=8, ones=3}
      

   2. Create a moreFives :: Wallet -> Int -> Wallet function that increases the number of fives.

       check_moreFives = (moreFives (Wallet 2 8) 3) == Wallet 5 8
      

4. (Simple updating) Given the data type definition:

    data Sherman = Sherman {a :: Int, b :: Int, c :: String}
      deriving (Show, Eq)
    ex2 = Sherman 10 50 "Them"
   

   1. How do you produce ex3 that is the same as ex2 except the a value is 30?

   2. Produce ex4 that is the same as ex3 except a is 5 and b is 55.