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Diffstat (limited to 'third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/Accum.hs')
-rw-r--r-- | third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/Accum.hs | 292 |
1 files changed, 0 insertions, 292 deletions
diff --git a/third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/Accum.hs b/third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/Accum.hs deleted file mode 100644 index 0a85c43f62bb..000000000000 --- a/third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/Accum.hs +++ /dev/null @@ -1,292 +0,0 @@ -{-# LANGUAGE CPP #-} -#if __GLASGOW_HASKELL__ >= 702 -{-# LANGUAGE Safe #-} -#endif -#if __GLASGOW_HASKELL__ >= 710 -{-# LANGUAGE AutoDeriveTypeable #-} -#endif ------------------------------------------------------------------------------ --- | --- Module : Control.Monad.Trans.Accum --- Copyright : (c) Nickolay Kudasov 2016 --- License : BSD-style (see the file LICENSE) --- --- Maintainer : R.Paterson@city.ac.uk --- Stability : experimental --- Portability : portable --- --- The lazy 'AccumT' monad transformer, which adds accumulation --- capabilities (such as declarations or document patches) to a given monad. --- --- This monad transformer provides append-only accumulation --- during the computation. For more general access, use --- "Control.Monad.Trans.State" instead. ------------------------------------------------------------------------------ - -module Control.Monad.Trans.Accum ( - -- * The Accum monad - Accum, - accum, - runAccum, - execAccum, - evalAccum, - mapAccum, - -- * The AccumT monad transformer - AccumT(AccumT), - runAccumT, - execAccumT, - evalAccumT, - mapAccumT, - -- * Accum operations - look, - looks, - add, - -- * Lifting other operations - liftCallCC, - liftCallCC', - liftCatch, - liftListen, - liftPass, - -- * Monad transformations - readerToAccumT, - writerToAccumT, - accumToStateT, - ) where - -import Control.Monad.IO.Class -import Control.Monad.Trans.Class -import Control.Monad.Trans.Reader (ReaderT(..)) -import Control.Monad.Trans.Writer (WriterT(..)) -import Control.Monad.Trans.State (StateT(..)) -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 -import Control.Monad.Signatures -#if !MIN_VERSION_base(4,8,0) -import Data.Monoid -#endif - --- --------------------------------------------------------------------------- --- | An accumulation monad parameterized by the type @w@ of output to accumulate. --- --- The 'return' function produces the output 'mempty', while @>>=@ --- combines the outputs of the subcomputations using 'mappend'. -type Accum w = AccumT w Identity - --- | Construct an accumulation computation from a (result, output) pair. --- (The inverse of 'runAccum'.) -accum :: (Monad m) => (w -> (a, w)) -> AccumT w m a -accum f = AccumT $ \ w -> return (f w) -{-# INLINE accum #-} - --- | Unwrap an accumulation computation as a (result, output) pair. --- (The inverse of 'accum'.) -runAccum :: Accum w a -> w -> (a, w) -runAccum m = runIdentity . runAccumT m -{-# INLINE runAccum #-} - --- | Extract the output from an accumulation computation. --- --- * @'execAccum' m w = 'snd' ('runAccum' m w)@ -execAccum :: Accum w a -> w -> w -execAccum m w = snd (runAccum m w) -{-# INLINE execAccum #-} - --- | Evaluate an accumulation computation with the given initial output history --- and return the final value, discarding the final output. --- --- * @'evalAccum' m w = 'fst' ('runAccum' m w)@ -evalAccum :: (Monoid w) => Accum w a -> w -> a -evalAccum m w = fst (runAccum m w) -{-# INLINE evalAccum #-} - --- | Map both the return value and output of a computation using --- the given function. --- --- * @'runAccum' ('mapAccum' f m) = f . 'runAccum' m@ -mapAccum :: ((a, w) -> (b, w)) -> Accum w a -> Accum w b -mapAccum f = mapAccumT (Identity . f . runIdentity) -{-# INLINE mapAccum #-} - --- --------------------------------------------------------------------------- --- | An accumulation monad parameterized by: --- --- * @w@ - the output to accumulate. --- --- * @m@ - The inner monad. --- --- The 'return' function produces the output 'mempty', while @>>=@ --- combines the outputs of the subcomputations using 'mappend'. --- --- This monad transformer is similar to both state and writer monad transformers. --- Thus it can be seen as --- --- * a restricted append-only version of a state monad transformer or --- --- * a writer monad transformer with the extra ability to read all previous output. -newtype AccumT w m a = AccumT (w -> m (a, w)) - --- | Unwrap an accumulation computation. -runAccumT :: AccumT w m a -> w -> m (a, w) -runAccumT (AccumT f) = f -{-# INLINE runAccumT #-} - --- | Extract the output from an accumulation computation. --- --- * @'execAccumT' m w = 'liftM' 'snd' ('runAccumT' m w)@ -execAccumT :: (Monad m) => AccumT w m a -> w -> m w -execAccumT m w = do - ~(_, w') <- runAccumT m w - return w' -{-# INLINE execAccumT #-} - --- | Evaluate an accumulation computation with the given initial output history --- and return the final value, discarding the final output. --- --- * @'evalAccumT' m w = 'liftM' 'fst' ('runAccumT' m w)@ -evalAccumT :: (Monad m, Monoid w) => AccumT w m a -> w -> m a -evalAccumT m w = do - ~(a, _) <- runAccumT m w - return a -{-# INLINE evalAccumT #-} - --- | Map both the return value and output of a computation using --- the given function. --- --- * @'runAccumT' ('mapAccumT' f m) = f . 'runAccumT' m@ -mapAccumT :: (m (a, w) -> n (b, w)) -> AccumT w m a -> AccumT w n b -mapAccumT f m = AccumT (f . runAccumT m) -{-# INLINE mapAccumT #-} - -instance (Functor m) => Functor (AccumT w m) where - fmap f = mapAccumT $ fmap $ \ ~(a, w) -> (f a, w) - {-# INLINE fmap #-} - -instance (Monoid w, Functor m, Monad m) => Applicative (AccumT w m) where - pure a = AccumT $ const $ return (a, mempty) - {-# INLINE pure #-} - mf <*> mv = AccumT $ \ w -> do - ~(f, w') <- runAccumT mf w - ~(v, w'') <- runAccumT mv (w `mappend` w') - return (f v, w' `mappend` w'') - {-# INLINE (<*>) #-} - -instance (Monoid w, Functor m, MonadPlus m) => Alternative (AccumT w m) where - empty = AccumT $ const mzero - {-# INLINE empty #-} - m <|> n = AccumT $ \ w -> runAccumT m w `mplus` runAccumT n w - {-# INLINE (<|>) #-} - -instance (Monoid w, Functor m, Monad m) => Monad (AccumT w m) where -#if !(MIN_VERSION_base(4,8,0)) - return a = AccumT $ const $ return (a, mempty) - {-# INLINE return #-} -#endif - m >>= k = AccumT $ \ w -> do - ~(a, w') <- runAccumT m w - ~(b, w'') <- runAccumT (k a) (w `mappend` w') - return (b, w' `mappend` w'') - {-# INLINE (>>=) #-} -#if !(MIN_VERSION_base(4,13,0)) - fail msg = AccumT $ const (fail msg) - {-# INLINE fail #-} -#endif - -#if MIN_VERSION_base(4,9,0) -instance (Monoid w, Fail.MonadFail m) => Fail.MonadFail (AccumT w m) where - fail msg = AccumT $ const (Fail.fail msg) - {-# INLINE fail #-} -#endif - -instance (Monoid w, Functor m, MonadPlus m) => MonadPlus (AccumT w m) where - mzero = AccumT $ const mzero - {-# INLINE mzero #-} - m `mplus` n = AccumT $ \ w -> runAccumT m w `mplus` runAccumT n w - {-# INLINE mplus #-} - -instance (Monoid w, Functor m, MonadFix m) => MonadFix (AccumT w m) where - mfix m = AccumT $ \ w -> mfix $ \ ~(a, _) -> runAccumT (m a) w - {-# INLINE mfix #-} - -instance (Monoid w) => MonadTrans (AccumT w) where - lift m = AccumT $ const $ do - a <- m - return (a, mempty) - {-# INLINE lift #-} - -instance (Monoid w, Functor m, MonadIO m) => MonadIO (AccumT w m) where - liftIO = lift . liftIO - {-# INLINE liftIO #-} - --- | @'look'@ is an action that fetches all the previously accumulated output. -look :: (Monoid w, Monad m) => AccumT w m w -look = AccumT $ \ w -> return (w, mempty) - --- | @'look'@ is an action that retrieves a function of the previously accumulated output. -looks :: (Monoid w, Monad m) => (w -> a) -> AccumT w m a -looks f = AccumT $ \ w -> return (f w, mempty) - --- | @'add' w@ is an action that produces the output @w@. -add :: (Monad m) => w -> AccumT w m () -add w = accum $ const ((), w) -{-# INLINE add #-} - --- | Uniform lifting of a @callCC@ operation to the new monad. --- This version rolls back to the original output history on entering the --- continuation. -liftCallCC :: CallCC m (a, w) (b, w) -> CallCC (AccumT w m) a b -liftCallCC callCC f = AccumT $ \ w -> - callCC $ \ c -> - runAccumT (f (\ a -> AccumT $ \ _ -> c (a, w))) w -{-# INLINE liftCallCC #-} - --- | In-situ lifting of a @callCC@ operation to the new monad. --- This version uses the current output history on entering the continuation. --- It does not satisfy the uniformity property (see "Control.Monad.Signatures"). -liftCallCC' :: CallCC m (a, w) (b, w) -> CallCC (AccumT w m) a b -liftCallCC' callCC f = AccumT $ \ s -> - callCC $ \ c -> - runAccumT (f (\ a -> AccumT $ \ s' -> c (a, s'))) s -{-# INLINE liftCallCC' #-} - --- | Lift a @catchE@ operation to the new monad. -liftCatch :: Catch e m (a, w) -> Catch e (AccumT w m) a -liftCatch catchE m h = - AccumT $ \ w -> runAccumT m w `catchE` \ e -> runAccumT (h e) w -{-# INLINE liftCatch #-} - --- | Lift a @listen@ operation to the new monad. -liftListen :: (Monad m) => Listen w m (a, s) -> Listen w (AccumT s m) a -liftListen listen m = AccumT $ \ s -> do - ~((a, s'), w) <- listen (runAccumT m s) - return ((a, w), s') -{-# INLINE liftListen #-} - --- | Lift a @pass@ operation to the new monad. -liftPass :: (Monad m) => Pass w m (a, s) -> Pass w (AccumT s m) a -liftPass pass m = AccumT $ \ s -> pass $ do - ~((a, f), s') <- runAccumT m s - return ((a, s'), f) -{-# INLINE liftPass #-} - --- | Convert a read-only computation into an accumulation computation. -readerToAccumT :: (Functor m, Monoid w) => ReaderT w m a -> AccumT w m a -readerToAccumT (ReaderT f) = AccumT $ \ w -> fmap (\ a -> (a, mempty)) (f w) -{-# INLINE readerToAccumT #-} - --- | Convert a writer computation into an accumulation computation. -writerToAccumT :: WriterT w m a -> AccumT w m a -writerToAccumT (WriterT m) = AccumT $ const $ m -{-# INLINE writerToAccumT #-} - --- | Convert an accumulation (append-only) computation into a fully --- stateful computation. -accumToStateT :: (Functor m, Monoid s) => AccumT s m a -> StateT s m a -accumToStateT (AccumT f) = - StateT $ \ w -> fmap (\ ~(a, w') -> (a, w `mappend` w')) (f w) -{-# INLINE accumToStateT #-} |