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Diffstat (limited to 'third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/RWS/CPS.hs')
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diff --git a/third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/RWS/CPS.hs b/third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/RWS/CPS.hs new file mode 100644 index 0000000000..8a565e1652 --- /dev/null +++ b/third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/RWS/CPS.hs @@ -0,0 +1,406 @@ +{-# LANGUAGE CPP #-} +#if __GLASGOW_HASKELL__ >= 702 +{-# LANGUAGE Safe #-} +#endif +#if __GLASGOW_HASKELL__ >= 710 +{-# LANGUAGE AutoDeriveTypeable #-} +#endif +----------------------------------------------------------------------------- +-- | +-- Module : Control.Monad.Trans.RWS.CPS +-- Copyright : (c) Daniel Mendler 2016, +-- (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 +-- +-- A monad transformer that combines 'ReaderT', 'WriterT' and 'StateT'. +-- This version uses continuation-passing-style for the writer part +-- to achieve constant space usage. +-- For a lazy version with the same interface, +-- see "Control.Monad.Trans.RWS.Lazy". +----------------------------------------------------------------------------- + +module Control.Monad.Trans.RWS.CPS ( + -- * The RWS monad + RWS, + rws, + runRWS, + evalRWS, + execRWS, + mapRWS, + withRWS, + -- * The RWST monad transformer + RWST, + rwsT, + runRWST, + evalRWST, + execRWST, + mapRWST, + withRWST, + -- * Reader operations + reader, + ask, + local, + asks, + -- * Writer operations + writer, + tell, + listen, + listens, + pass, + censor, + -- * State operations + state, + get, + put, + modify, + gets, + -- * Lifting other operations + liftCallCC, + liftCallCC', + liftCatch, + ) where + +import Control.Applicative +import Control.Monad +import Control.Monad.Fix +import Control.Monad.IO.Class +import Control.Monad.Trans.Class +import Control.Monad.Signatures +import Data.Functor.Identity + +#if !(MIN_VERSION_base(4,8,0)) +import Data.Monoid +#endif + +#if MIN_VERSION_base(4,9,0) +import qualified Control.Monad.Fail as Fail +#endif + +-- | A monad containing an environment of type @r@, output of type @w@ +-- and an updatable state of type @s@. +type RWS r w s = RWST r w s Identity + +-- | Construct an RWS computation from a function. +-- (The inverse of 'runRWS'.) +rws :: (Monoid w) => (r -> s -> (a, s, w)) -> RWS r w s a +rws f = RWST $ \ r s w -> + let (a, s', w') = f r s; wt = w `mappend` w' in wt `seq` return (a, s', wt) +{-# INLINE rws #-} + +-- | Unwrap an RWS computation as a function. +-- (The inverse of 'rws'.) +runRWS :: (Monoid w) => RWS r w s a -> r -> s -> (a, s, w) +runRWS m r s = runIdentity (runRWST m r s) +{-# INLINE runRWS #-} + +-- | Evaluate a computation with the given initial state and environment, +-- returning the final value and output, discarding the final state. +evalRWS :: (Monoid w) + => RWS r w s a -- ^RWS computation to execute + -> r -- ^initial environment + -> s -- ^initial value + -> (a, w) -- ^final value and output +evalRWS m r s = let + (a, _, w) = runRWS m r s + in (a, w) +{-# INLINE evalRWS #-} + +-- | Evaluate a computation with the given initial state and environment, +-- returning the final state and output, discarding the final value. +execRWS :: (Monoid w) + => RWS r w s a -- ^RWS computation to execute + -> r -- ^initial environment + -> s -- ^initial value + -> (s, w) -- ^final state and output +execRWS m r s = let + (_, s', w) = runRWS m r s + in (s', w) +{-# INLINE execRWS #-} + +-- | Map the return value, final state and output of a computation using +-- the given function. +-- +-- * @'runRWS' ('mapRWS' f m) r s = f ('runRWS' m r s)@ +mapRWS :: (Monoid w, Monoid w') => ((a, s, w) -> (b, s, w')) -> RWS r w s a -> RWS r w' s b +mapRWS f = mapRWST (Identity . f . runIdentity) +{-# INLINE mapRWS #-} + +-- | @'withRWS' f m@ executes action @m@ with an initial environment +-- and state modified by applying @f@. +-- +-- * @'runRWS' ('withRWS' f m) r s = 'uncurry' ('runRWS' m) (f r s)@ +withRWS :: (r' -> s -> (r, s)) -> RWS r w s a -> RWS r' w s a +withRWS = withRWST +{-# INLINE withRWS #-} + +-- --------------------------------------------------------------------------- +-- | A monad transformer adding reading an environment of type @r@, +-- collecting an output of type @w@ and updating a state of type @s@ +-- to an inner monad @m@. +newtype RWST r w s m a = RWST { unRWST :: r -> s -> w -> m (a, s, w) } + +-- | Construct an RWST computation from a function. +-- (The inverse of 'runRWST'.) +rwsT :: (Functor m, Monoid w) => (r -> s -> m (a, s, w)) -> RWST r w s m a +rwsT f = RWST $ \ r s w -> + (\ (a, s', w') -> let wt = w `mappend` w' in wt `seq` (a, s', wt)) <$> f r s +{-# INLINE rwsT #-} + +-- | Unwrap an RWST computation as a function. +-- (The inverse of 'rwsT'.) +runRWST :: (Monoid w) => RWST r w s m a -> r -> s -> m (a, s, w) +runRWST m r s = unRWST m r s mempty +{-# INLINE runRWST #-} + +-- | Evaluate a computation with the given initial state and environment, +-- returning the final value and output, discarding the final state. +evalRWST :: (Monad m, Monoid w) + => RWST r w s m a -- ^computation to execute + -> r -- ^initial environment + -> s -- ^initial value + -> m (a, w) -- ^computation yielding final value and output +evalRWST m r s = do + (a, _, w) <- runRWST m r s + return (a, w) +{-# INLINE evalRWST #-} + +-- | Evaluate a computation with the given initial state and environment, +-- returning the final state and output, discarding the final value. +execRWST :: (Monad m, Monoid w) + => RWST r w s m a -- ^computation to execute + -> r -- ^initial environment + -> s -- ^initial value + -> m (s, w) -- ^computation yielding final state and output +execRWST m r s = do + (_, s', w) <- runRWST m r s + return (s', w) +{-# INLINE execRWST #-} + +-- | Map the inner computation using the given function. +-- +-- * @'runRWST' ('mapRWST' f m) r s = f ('runRWST' m r s)@ +--mapRWST :: (m (a, s, w) -> n (b, s, w')) -> RWST r w s m a -> RWST r w' s n b +mapRWST :: (Monad n, Monoid w, Monoid w') => + (m (a, s, w) -> n (b, s, w')) -> RWST r w s m a -> RWST r w' s n b +mapRWST f m = RWST $ \ r s w -> do + (a, s', w') <- f (runRWST m r s) + let wt = w `mappend` w' + wt `seq` return (a, s', wt) +{-# INLINE mapRWST #-} + +-- | @'withRWST' f m@ executes action @m@ with an initial environment +-- and state modified by applying @f@. +-- +-- * @'runRWST' ('withRWST' f m) r s = 'uncurry' ('runRWST' m) (f r s)@ +withRWST :: (r' -> s -> (r, s)) -> RWST r w s m a -> RWST r' w s m a +withRWST f m = RWST $ \ r s -> uncurry (unRWST m) (f r s) +{-# INLINE withRWST #-} + +instance (Functor m) => Functor (RWST r w s m) where + fmap f m = RWST $ \ r s w -> (\ (a, s', w') -> (f a, s', w')) <$> unRWST m r s w + {-# INLINE fmap #-} + +instance (Functor m, Monad m) => Applicative (RWST r w s m) where + pure a = RWST $ \ _ s w -> return (a, s, w) + {-# INLINE pure #-} + + RWST mf <*> RWST mx = RWST $ \ r s w -> do + (f, s', w') <- mf r s w + (x, s'', w'') <- mx r s' w' + return (f x, s'', w'') + {-# INLINE (<*>) #-} + +instance (Functor m, MonadPlus m) => Alternative (RWST r w s m) where + empty = RWST $ \ _ _ _ -> mzero + {-# INLINE empty #-} + + RWST m <|> RWST n = RWST $ \ r s w -> m r s w `mplus` n r s w + {-# INLINE (<|>) #-} + +instance (Monad m) => Monad (RWST r w s m) where +#if !(MIN_VERSION_base(4,8,0)) + return a = RWST $ \ _ s w -> return (a, s, w) + {-# INLINE return #-} +#endif + + m >>= k = RWST $ \ r s w -> do + (a, s', w') <- unRWST m r s w + unRWST (k a) r s' w' + {-# INLINE (>>=) #-} + +#if !(MIN_VERSION_base(4,13,0)) + fail msg = RWST $ \ _ _ _ -> fail msg + {-# INLINE fail #-} +#endif + +#if MIN_VERSION_base(4,9,0) +instance (Fail.MonadFail m) => Fail.MonadFail (RWST r w s m) where + fail msg = RWST $ \ _ _ _ -> Fail.fail msg + {-# INLINE fail #-} +#endif + +instance (Functor m, MonadPlus m) => MonadPlus (RWST r w s m) where + mzero = empty + {-# INLINE mzero #-} + mplus = (<|>) + {-# INLINE mplus #-} + +instance (MonadFix m) => MonadFix (RWST r w s m) where + mfix f = RWST $ \ r s w -> mfix $ \ ~(a, _, _) -> unRWST (f a) r s w + {-# INLINE mfix #-} + +instance MonadTrans (RWST r w s) where + lift m = RWST $ \ _ s w -> do + a <- m + return (a, s, w) + {-# INLINE lift #-} + +instance (MonadIO m) => MonadIO (RWST r w s m) where + liftIO = lift . liftIO + {-# INLINE liftIO #-} +-- --------------------------------------------------------------------------- +-- Reader operations + +-- | Constructor for computations in the reader monad (equivalent to 'asks'). +reader :: (Monad m) => (r -> a) -> RWST r w s m a +reader = asks +{-# INLINE reader #-} + +-- | Fetch the value of the environment. +ask :: (Monad m) => RWST r w s m r +ask = asks id +{-# INLINE ask #-} + +-- | Execute a computation in a modified environment +-- +-- * @'runRWST' ('local' f m) r s = 'runRWST' m (f r) s@ +local :: (r -> r) -> RWST r w s m a -> RWST r w s m a +local f m = RWST $ \ r s w -> unRWST m (f r) s w +{-# INLINE local #-} + +-- | Retrieve a function of the current environment. +-- +-- * @'asks' f = 'liftM' f 'ask'@ +asks :: (Monad m) => (r -> a) -> RWST r w s m a +asks f = RWST $ \ r s w -> return (f r, s, w) +{-# INLINE asks #-} + +-- --------------------------------------------------------------------------- +-- Writer operations + +-- | Construct a writer computation from a (result, output) pair. +writer :: (Monoid w, Monad m) => (a, w) -> RWST r w s m a +writer (a, w') = RWST $ \ _ s w -> let wt = w `mappend` w' in wt `seq` return (a, s, wt) +{-# INLINE writer #-} + +-- | @'tell' w@ is an action that produces the output @w@. +tell :: (Monoid w, Monad m) => w -> RWST r w s m () +tell w' = writer ((), w') +{-# INLINE tell #-} + +-- | @'listen' m@ is an action that executes the action @m@ and adds its +-- output to the value of the computation. +-- +-- * @'runRWST' ('listen' m) r s = 'liftM' (\\ (a, w) -> ((a, w), w)) ('runRWST' m r s)@ +listen :: (Monoid w, Monad m) => RWST r w s m a -> RWST r w s m (a, w) +listen = listens id +{-# INLINE listen #-} + +-- | @'listens' f m@ is an action that executes the action @m@ and adds +-- the result of applying @f@ to the output to the value of the computation. +-- +-- * @'listens' f m = 'liftM' (id *** f) ('listen' m)@ +-- +-- * @'runRWST' ('listens' f m) r s = 'liftM' (\\ (a, w) -> ((a, f w), w)) ('runRWST' m r s)@ +listens :: (Monoid w, Monad m) => (w -> b) -> RWST r w s m a -> RWST r w s m (a, b) +listens f m = RWST $ \ r s w -> do + (a, s', w') <- runRWST m r s + let wt = w `mappend` w' + wt `seq` return ((a, f w'), s', wt) +{-# INLINE listens #-} + +-- | @'pass' m@ is an action that executes the action @m@, which returns +-- a value and a function, and returns the value, applying the function +-- to the output. +-- +-- * @'runRWST' ('pass' m) r s = 'liftM' (\\ ((a, f), w) -> (a, f w)) ('runRWST' m r s)@ +pass :: (Monoid w, Monoid w', Monad m) => RWST r w s m (a, w -> w') -> RWST r w' s m a +pass m = RWST $ \ r s w -> do + ((a, f), s', w') <- runRWST m r s + let wt = w `mappend` f w' + wt `seq` return (a, s', wt) +{-# INLINE pass #-} + +-- | @'censor' f m@ is an action that executes the action @m@ and +-- applies the function @f@ to its output, leaving the return value +-- unchanged. +-- +-- * @'censor' f m = 'pass' ('liftM' (\\ x -> (x,f)) m)@ +-- +-- * @'runRWST' ('censor' f m) r s = 'liftM' (\\ (a, w) -> (a, f w)) ('runRWST' m r s)@ +censor :: (Monoid w, Monad m) => (w -> w) -> RWST r w s m a -> RWST r w s m a +censor f m = RWST $ \ r s w -> do + (a, s', w') <- runRWST m r s + let wt = w `mappend` f w' + wt `seq` return (a, s', wt) +{-# INLINE censor #-} + +-- --------------------------------------------------------------------------- +-- State operations + +-- | Construct a state monad computation from a state transformer function. +state :: (Monad m) => (s -> (a, s)) -> RWST r w s m a +state f = RWST $ \ _ s w -> let (a, s') = f s in return (a, s', w) +{-# INLINE state #-} + +-- | Fetch the current value of the state within the monad. +get :: (Monad m) =>RWST r w s m s +get = gets id +{-# INLINE get #-} + +-- | @'put' s@ sets the state within the monad to @s@. +put :: (Monad m) =>s -> RWST r w s m () +put s = RWST $ \ _ _ w -> return ((), s, w) +{-# INLINE put #-} + +-- | @'modify' f@ is an action that updates the state to the result of +-- applying @f@ to the current state. +-- +-- * @'modify' f = 'get' >>= ('put' . f)@ +modify :: (Monad m) =>(s -> s) -> RWST r w s m () +modify f = RWST $ \ _ s w -> return ((), f s, w) +{-# INLINE modify #-} + +-- | Get a specific component of the state, using a projection function +-- supplied. +-- +-- * @'gets' f = 'liftM' f 'get'@ +gets :: (Monad m) =>(s -> a) -> RWST r w s m a +gets f = RWST $ \ _ s w -> return (f s, s, w) +{-# INLINE gets #-} + +-- | Uniform lifting of a @callCC@ operation to the new monad. +-- This version rolls back to the original state on entering the +-- continuation. +liftCallCC :: CallCC m (a,s,w) (b,s,w) -> CallCC (RWST r w s m) a b +liftCallCC callCC f = RWST $ \ r s w -> + callCC $ \ c -> unRWST (f (\ a -> RWST $ \ _ _ _ -> c (a, s, w))) r s w +{-# INLINE liftCallCC #-} + +-- | In-situ lifting of a @callCC@ operation to the new monad. +-- This version uses the current state on entering the continuation. +liftCallCC' :: CallCC m (a,s,w) (b,s,w) -> CallCC (RWST r w s m) a b +liftCallCC' callCC f = RWST $ \ r s w -> + callCC $ \ c -> unRWST (f (\ a -> RWST $ \ _ s' _ -> c (a, s', w))) r s w +{-# INLINE liftCallCC' #-} + +-- | Lift a @catchE@ operation to the new monad. +liftCatch :: Catch e m (a,s,w) -> Catch e (RWST r w s m) a +liftCatch catchE m h = + RWST $ \ r s w -> unRWST m r s w `catchE` \ e -> unRWST (h e) r s w +{-# INLINE liftCatch #-} |