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module MonadTransformersScratch where
import Control.Monad
import qualified Control.Monad.Trans.Maybe as M
import qualified Control.Monad.Trans.Reader as R
import qualified Control.Monad.Trans.State as S
import Data.Function ((&))
--------------------------------------------------------------------------------
newtype MaybeT m a =
MaybeT { runMaybeT :: m (Maybe a) }
instance (Functor f) => Functor (MaybeT f) where
fmap f (MaybeT run) =
MaybeT $ (fmap . fmap) f run
instance (Applicative m) => Applicative (MaybeT m) where
pure x = x & pure & pure & MaybeT
_ <*> _ = undefined
instance (Monad m) => Monad (MaybeT m) where
return = pure
(MaybeT ma) >>= f = MaybeT $ do
maybeX <- ma
case maybeX of
Nothing -> pure Nothing
Just x -> x & f & runMaybeT
--------------------------------------------------------------------------------
newtype EitherT e m a =
EitherT { runEitherT :: m (Either e a) }
instance (Functor m) => Functor (EitherT e m) where
fmap f (EitherT mEither) =
EitherT $ (fmap . fmap) f mEither
instance (Applicative m) => Applicative (EitherT e m) where
pure x = EitherT $ (pure . pure) x
EitherT mEitherF <*> EitherT mEitherX =
EitherT $ (fmap (<*>) mEitherF) <*> mEitherX
instance (Monad m) => Monad (EitherT e m) where
return = pure
EitherT mEitherX >>= f = EitherT $ do
eitherX <- mEitherX
case eitherX of
Left x -> pure $ Left x
Right x -> runEitherT $ f x
swapEither :: Either l r -> Either r l
swapEither (Left x) = Right x
swapEither (Right x) = Left x
swapEitherT :: (Functor m) => EitherT e m a -> EitherT a m e
swapEitherT (EitherT mEitherX) =
EitherT $ fmap swapEither mEitherX
eitherT :: Monad m => (a -> m c) -> (b -> m c) -> EitherT a m b -> m c
eitherT aToMC bToMC (EitherT mEitherX) = do
eitherX <- mEitherX
case eitherX of
Left x -> aToMC x
Right x -> bToMC x
--------------------------------------------------------------------------------
newtype ReaderT r m a = ReaderT { runReaderT :: r -> m a }
instance (Functor m) => Functor (ReaderT r m) where
fmap f (ReaderT rma) =
ReaderT $ (fmap . fmap) f rma
instance (Applicative m) => Applicative (ReaderT r m) where
pure x = x & pure & pure & ReaderT
ReaderT f <*> ReaderT x = ReaderT $ fmap (<*>) f <*> x
-- instance (Monad m) => Monad (ReaderT r m) where
-- return = pure
-- ReaderT rma >>= f =
-- ReaderT $ \r -> do
-- a <- rma r
-- runReaderT (f a) r
-- --------------------------------------------------------------------------------
rDec :: Num a => R.Reader a a
rDec = R.ReaderT $ \x -> pure $ x + 1
rShow :: Show a => R.Reader a String
rShow = R.ReaderT $ \x -> pure $ show x
rPrintAndInc :: (Num a, Show a) => R.ReaderT a IO a
rPrintAndInc = R.ReaderT $ \x ->
putStrLn ("Hi: " ++ show x) >> pure (x + 1)
sPrintIncAccum :: (Num a, Show a) => S.StateT a IO String
sPrintIncAccum = S.StateT $ \x -> do
putStrLn ("Hi: " ++ show x)
pure (show x, x + 1)
--------------------------------------------------------------------------------
isValid :: String -> Bool
isValid v = '!' `elem` v
maybeExcite :: M.MaybeT IO String
maybeExcite = M.MaybeT $ do
x <- getLine
putStrLn ""
case isValid x of
False -> pure Nothing
True -> pure $ Just x
doExcite :: IO ()
doExcite = do
putStr "Say something *exciting*: "
excite <- M.runMaybeT maybeExcite
case excite of
Nothing -> putStrLn "Gonna need some more excitement..."
Just x -> putStrLn "Now THAT'S exciting...nice!"
--------------------------------------------------------------------------------
data Participant
= Man
| Machine
deriving (Show, Eq)
newtype Hand = Hand (Integer, Integer) deriving (Show, Eq)
newtype Score = Score (Integer, Integer) deriving (Show, Eq)
getLineLn :: String -> IO String
getLineLn prompt = do
putStr prompt
x <- getLine
putStrLn ""
pure x
promptGuess :: IO Hand
promptGuess = do
fingers <- getLineLn "How many fingers (0-5): "
guess <- getLineLn "Guess: "
pure $ Hand (read guess, read fingers)
aiGuess :: IO Hand
aiGuess = pure $ Hand (2, 3)
whoWon :: Hand -> Hand -> Maybe Participant
whoWon (Hand (guessA, fingersA)) (Hand (guessB, fingersB))
| guessA == guessB && guessA == (fingersA + fingersB) = Nothing
| guessA == (fingersA + fingersB) = Just Man
| guessB == (fingersA + fingersB) = Just Machine
| otherwise = Nothing
initScore :: Score
initScore = Score (0, 0)
printScore :: Score -> IO ()
printScore (Score (man, machine)) =
putStrLn $ "Man: " ++ show man ++ " Machine: " ++ show machine
startMorra :: S.StateT Score IO ()
startMorra = S.StateT $ \(Score (man, machine)) -> do
Hand (guessA, fingersA) <- promptGuess
Hand (guessB, fingersB) <- aiGuess
putStrLn $ "P: " ++ show fingersA ++ "," ++ show guessA
putStrLn $ "C: " ++ show fingersB ++ "," ++ show guessB
case whoWon (Hand (guessA, fingersA)) (Hand (guessB, fingersB)) of
Nothing -> do
putStrLn "Nobody won..."
printScore (Score (man, machine))
pure ((), Score (man, machine))
Just Man -> do
putStrLn "Man won!"
printScore (Score (man + 1, machine))
pure ((), Score (man + 1, machine))
Just Machine -> do
putStrLn "Oh no... Machine won..."
printScore (Score (man, machine + 1))
pure ((), Score (man, machine + 1))
playMorra = S.runStateT (forever startMorra) initScore
|
