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Diffstat (limited to 'third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/Reader.hs')
| -rw-r--r-- | third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/Reader.hs | 262 |
1 files changed, 0 insertions, 262 deletions
diff --git a/third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/Reader.hs b/third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/Reader.hs deleted file mode 100644 index 25e3ad27c3..0000000000 --- a/third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/Reader.hs +++ /dev/null @@ -1,262 +0,0 @@ -{-# LANGUAGE CPP #-} -#if __GLASGOW_HASKELL__ >= 702 -{-# LANGUAGE Safe #-} -#endif -#if __GLASGOW_HASKELL__ >= 710 -{-# LANGUAGE AutoDeriveTypeable #-} -#endif ------------------------------------------------------------------------------ --- | --- Module : Control.Monad.Trans.Reader --- Copyright : (c) Andy Gill 2001, --- (c) Oregon Graduate Institute of Science and Technology, 2001 --- License : BSD-style (see the file LICENSE) --- --- Maintainer : R.Paterson@city.ac.uk --- Stability : experimental --- Portability : portable --- --- Declaration of the 'ReaderT' monad transformer, which adds a static --- environment to a given monad. --- --- If the computation is to modify the stored information, use --- "Control.Monad.Trans.State" instead. ------------------------------------------------------------------------------ - -module Control.Monad.Trans.Reader ( - -- * The Reader monad - Reader, - reader, - runReader, - mapReader, - withReader, - -- * The ReaderT monad transformer - ReaderT(..), - mapReaderT, - withReaderT, - -- * Reader operations - ask, - local, - asks, - -- * Lifting other operations - liftCallCC, - liftCatch, - ) where - -import Control.Monad.IO.Class -import Control.Monad.Signatures -import Control.Monad.Trans.Class -#if MIN_VERSION_base(4,12,0) -import Data.Functor.Contravariant -#endif -import Data.Functor.Identity - -import Control.Applicative -import Control.Monad -#if MIN_VERSION_base(4,9,0) -import qualified Control.Monad.Fail as Fail -#endif -import Control.Monad.Fix -#if !(MIN_VERSION_base(4,6,0)) -import Control.Monad.Instances () -- deprecated from base-4.6 -#endif -#if MIN_VERSION_base(4,4,0) -import Control.Monad.Zip (MonadZip(mzipWith)) -#endif -#if MIN_VERSION_base(4,2,0) -import Data.Functor(Functor(..)) -#endif - --- | The parameterizable reader monad. --- --- Computations are functions of a shared environment. --- --- The 'return' function ignores the environment, while @>>=@ passes --- the inherited environment to both subcomputations. -type Reader r = ReaderT r Identity - --- | Constructor for computations in the reader monad (equivalent to 'asks'). -reader :: (Monad m) => (r -> a) -> ReaderT r m a -reader f = ReaderT (return . f) -{-# INLINE reader #-} - --- | Runs a @Reader@ and extracts the final value from it. --- (The inverse of 'reader'.) -runReader - :: Reader r a -- ^ A @Reader@ to run. - -> r -- ^ An initial environment. - -> a -runReader m = runIdentity . runReaderT m -{-# INLINE runReader #-} - --- | Transform the value returned by a @Reader@. --- --- * @'runReader' ('mapReader' f m) = f . 'runReader' m@ -mapReader :: (a -> b) -> Reader r a -> Reader r b -mapReader f = mapReaderT (Identity . f . runIdentity) -{-# INLINE mapReader #-} - --- | Execute a computation in a modified environment --- (a specialization of 'withReaderT'). --- --- * @'runReader' ('withReader' f m) = 'runReader' m . f@ -withReader - :: (r' -> r) -- ^ The function to modify the environment. - -> Reader r a -- ^ Computation to run in the modified environment. - -> Reader r' a -withReader = withReaderT -{-# INLINE withReader #-} - --- | The reader monad transformer, --- which adds a read-only environment to the given monad. --- --- The 'return' function ignores the environment, while @>>=@ passes --- the inherited environment to both subcomputations. -newtype ReaderT r m a = ReaderT { runReaderT :: r -> m a } - --- | Transform the computation inside a @ReaderT@. --- --- * @'runReaderT' ('mapReaderT' f m) = f . 'runReaderT' m@ -mapReaderT :: (m a -> n b) -> ReaderT r m a -> ReaderT r n b -mapReaderT f m = ReaderT $ f . runReaderT m -{-# INLINE mapReaderT #-} - --- | Execute a computation in a modified environment --- (a more general version of 'local'). --- --- * @'runReaderT' ('withReaderT' f m) = 'runReaderT' m . f@ -withReaderT - :: (r' -> r) -- ^ The function to modify the environment. - -> ReaderT r m a -- ^ Computation to run in the modified environment. - -> ReaderT r' m a -withReaderT f m = ReaderT $ runReaderT m . f -{-# INLINE withReaderT #-} - -instance (Functor m) => Functor (ReaderT r m) where - fmap f = mapReaderT (fmap f) - {-# INLINE fmap #-} -#if MIN_VERSION_base(4,2,0) - x <$ v = mapReaderT (x <$) v - {-# INLINE (<$) #-} -#endif - -instance (Applicative m) => Applicative (ReaderT r m) where - pure = liftReaderT . pure - {-# INLINE pure #-} - f <*> v = ReaderT $ \ r -> runReaderT f r <*> runReaderT v r - {-# INLINE (<*>) #-} -#if MIN_VERSION_base(4,2,0) - u *> v = ReaderT $ \ r -> runReaderT u r *> runReaderT v r - {-# INLINE (*>) #-} - u <* v = ReaderT $ \ r -> runReaderT u r <* runReaderT v r - {-# INLINE (<*) #-} -#endif -#if MIN_VERSION_base(4,10,0) - liftA2 f x y = ReaderT $ \ r -> liftA2 f (runReaderT x r) (runReaderT y r) - {-# INLINE liftA2 #-} -#endif - -instance (Alternative m) => Alternative (ReaderT r m) where - empty = liftReaderT empty - {-# INLINE empty #-} - m <|> n = ReaderT $ \ r -> runReaderT m r <|> runReaderT n r - {-# INLINE (<|>) #-} - -instance (Monad m) => Monad (ReaderT r m) where -#if !(MIN_VERSION_base(4,8,0)) - return = lift . return - {-# INLINE return #-} -#endif - m >>= k = ReaderT $ \ r -> do - a <- runReaderT m r - runReaderT (k a) r - {-# INLINE (>>=) #-} -#if MIN_VERSION_base(4,8,0) - (>>) = (*>) -#else - m >> k = ReaderT $ \ r -> runReaderT m r >> runReaderT k r -#endif - {-# INLINE (>>) #-} -#if !(MIN_VERSION_base(4,13,0)) - fail msg = lift (fail msg) - {-# INLINE fail #-} -#endif - -#if MIN_VERSION_base(4,9,0) -instance (Fail.MonadFail m) => Fail.MonadFail (ReaderT r m) where - fail msg = lift (Fail.fail msg) - {-# INLINE fail #-} -#endif - -instance (MonadPlus m) => MonadPlus (ReaderT r m) where - mzero = lift mzero - {-# INLINE mzero #-} - m `mplus` n = ReaderT $ \ r -> runReaderT m r `mplus` runReaderT n r - {-# INLINE mplus #-} - -instance (MonadFix m) => MonadFix (ReaderT r m) where - mfix f = ReaderT $ \ r -> mfix $ \ a -> runReaderT (f a) r - {-# INLINE mfix #-} - -instance MonadTrans (ReaderT r) where - lift = liftReaderT - {-# INLINE lift #-} - -instance (MonadIO m) => MonadIO (ReaderT r m) where - liftIO = lift . liftIO - {-# INLINE liftIO #-} - -#if MIN_VERSION_base(4,4,0) -instance (MonadZip m) => MonadZip (ReaderT r m) where - mzipWith f (ReaderT m) (ReaderT n) = ReaderT $ \ a -> - mzipWith f (m a) (n a) - {-# INLINE mzipWith #-} -#endif - -#if MIN_VERSION_base(4,12,0) -instance Contravariant m => Contravariant (ReaderT r m) where - contramap f = ReaderT . fmap (contramap f) . runReaderT - {-# INLINE contramap #-} -#endif - -liftReaderT :: m a -> ReaderT r m a -liftReaderT m = ReaderT (const m) -{-# INLINE liftReaderT #-} - --- | Fetch the value of the environment. -ask :: (Monad m) => ReaderT r m r -ask = ReaderT return -{-# INLINE ask #-} - --- | Execute a computation in a modified environment --- (a specialization of 'withReaderT'). --- --- * @'runReaderT' ('local' f m) = 'runReaderT' m . f@ -local - :: (r -> r) -- ^ The function to modify the environment. - -> ReaderT r m a -- ^ Computation to run in the modified environment. - -> ReaderT r m a -local = withReaderT -{-# INLINE local #-} - --- | Retrieve a function of the current environment. --- --- * @'asks' f = 'liftM' f 'ask'@ -asks :: (Monad m) - => (r -> a) -- ^ The selector function to apply to the environment. - -> ReaderT r m a -asks f = ReaderT (return . f) -{-# INLINE asks #-} - --- | Lift a @callCC@ operation to the new monad. -liftCallCC :: CallCC m a b -> CallCC (ReaderT r m) a b -liftCallCC callCC f = ReaderT $ \ r -> - callCC $ \ c -> - runReaderT (f (ReaderT . const . c)) r -{-# INLINE liftCallCC #-} - --- | Lift a @catchE@ operation to the new monad. -liftCatch :: Catch e m a -> Catch e (ReaderT r m) a -liftCatch f m h = - ReaderT $ \ r -> f (runReaderT m r) (\ e -> runReaderT (h e) r) -{-# INLINE liftCatch #-} |