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Diffstat (limited to 'third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/RWS/Lazy.hs')
| -rw-r--r-- | third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/RWS/Lazy.hs | 389 |
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diff --git a/third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/RWS/Lazy.hs b/third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/RWS/Lazy.hs new file mode 100644 index 0000000000..8f98b2c5e0 --- /dev/null +++ b/third_party/bazel/rules_haskell/examples/transformers/Control/Monad/Trans/RWS/Lazy.hs @@ -0,0 +1,389 @@ +{-# LANGUAGE CPP #-} +#if __GLASGOW_HASKELL__ >= 702 +{-# LANGUAGE Safe #-} +#endif +#if __GLASGOW_HASKELL__ >= 710 +{-# LANGUAGE AutoDeriveTypeable #-} +#endif +----------------------------------------------------------------------------- +-- | +-- Module : Control.Monad.Trans.RWS.Lazy +-- 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 +-- +-- A monad transformer that combines 'ReaderT', 'WriterT' and 'StateT'. +-- This version is lazy; for a constant-space version with almost the +-- same interface, see "Control.Monad.Trans.RWS.CPS". +----------------------------------------------------------------------------- + +module Control.Monad.Trans.RWS.Lazy ( + -- * The RWS monad + RWS, + rws, + runRWS, + evalRWS, + execRWS, + mapRWS, + withRWS, + -- * The RWST monad transformer + RWST(..), + 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.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 +import Data.Monoid + +-- | 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 :: (r -> s -> (a, s, w)) -> RWS r w s a +rws f = RWST (\ r s -> Identity (f r s)) +{-# INLINE rws #-} + +-- | Unwrap an RWS computation as a function. +-- (The inverse of 'rws'.) +runRWS :: 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 :: 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 :: 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 :: ((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 { runRWST :: r -> s -> m (a, s, w) } + +-- | Evaluate a computation with the given initial state and environment, +-- returning the final value and output, discarding the final state. +evalRWST :: (Monad m) + => 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) + => 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 f m = RWST $ \ r s -> f (runRWST m r s) +{-# 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 (runRWST m) (f r s) +{-# INLINE withRWST #-} + +instance (Functor m) => Functor (RWST r w s m) where + fmap f m = RWST $ \ r s -> + fmap (\ ~(a, s', w) -> (f a, s', w)) $ runRWST m r s + {-# INLINE fmap #-} + +instance (Monoid w, Functor m, Monad m) => Applicative (RWST r w s m) where + pure a = RWST $ \ _ s -> return (a, s, mempty) + {-# INLINE pure #-} + RWST mf <*> RWST mx = RWST $ \ r s -> do + ~(f, s', w) <- mf r s + ~(x, s'',w') <- mx r s' + return (f x, s'', w `mappend` w') + {-# INLINE (<*>) #-} + +instance (Monoid w, Functor m, MonadPlus m) => Alternative (RWST r w s m) where + empty = RWST $ \ _ _ -> mzero + {-# INLINE empty #-} + RWST m <|> RWST n = RWST $ \ r s -> m r s `mplus` n r s + {-# INLINE (<|>) #-} + +instance (Monoid w, Monad m) => Monad (RWST r w s m) where +#if !(MIN_VERSION_base(4,8,0)) + return a = RWST $ \ _ s -> return (a, s, mempty) + {-# INLINE return #-} +#endif + m >>= k = RWST $ \ r s -> do + ~(a, s', w) <- runRWST m r s + ~(b, s'',w') <- runRWST (k a) r s' + return (b, s'', w `mappend` 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 (Monoid w, Fail.MonadFail m) => Fail.MonadFail (RWST r w s m) where + fail msg = RWST $ \ _ _ -> Fail.fail msg + {-# INLINE fail #-} +#endif + +instance (Monoid w, MonadPlus m) => MonadPlus (RWST r w s m) where + mzero = RWST $ \ _ _ -> mzero + {-# INLINE mzero #-} + RWST m `mplus` RWST n = RWST $ \ r s -> m r s `mplus` n r s + {-# INLINE mplus #-} + +instance (Monoid w, MonadFix m) => MonadFix (RWST r w s m) where + mfix f = RWST $ \ r s -> mfix $ \ ~(a, _, _) -> runRWST (f a) r s + {-# INLINE mfix #-} + +instance (Monoid w) => MonadTrans (RWST r w s) where + lift m = RWST $ \ _ s -> do + a <- m + return (a, s, mempty) + {-# INLINE lift #-} + +instance (Monoid w, MonadIO m) => MonadIO (RWST r w s m) where + liftIO = lift . liftIO + {-# INLINE liftIO #-} + +#if MIN_VERSION_base(4,12,0) +instance Contravariant m => Contravariant (RWST r w s m) where + contramap f m = RWST $ \r s -> + contramap (\ ~(a, s', w) -> (f a, s', w)) $ runRWST m r s + {-# INLINE contramap #-} +#endif + +-- --------------------------------------------------------------------------- +-- Reader operations + +-- | Constructor for computations in the reader monad (equivalent to 'asks'). +reader :: (Monoid w, Monad m) => (r -> a) -> RWST r w s m a +reader = asks +{-# INLINE reader #-} + +-- | Fetch the value of the environment. +ask :: (Monoid w, Monad m) => RWST r w s m r +ask = RWST $ \ r s -> return (r, s, mempty) +{-# 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 -> runRWST m (f r) s +{-# INLINE local #-} + +-- | Retrieve a function of the current environment. +-- +-- * @'asks' f = 'liftM' f 'ask'@ +asks :: (Monoid w, Monad m) => (r -> a) -> RWST r w s m a +asks f = RWST $ \ r s -> return (f r, s, mempty) +{-# INLINE asks #-} + +-- --------------------------------------------------------------------------- +-- Writer operations + +-- | Construct a writer computation from a (result, output) pair. +writer :: (Monad m) => (a, w) -> RWST r w s m a +writer (a, w) = RWST $ \ _ s -> return (a, s, w) +{-# INLINE writer #-} + +-- | @'tell' w@ is an action that produces the output @w@. +tell :: (Monad m) => w -> RWST r w s m () +tell w = RWST $ \ _ s -> return ((),s,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 :: (Monad m) => RWST r w s m a -> RWST r w s m (a, w) +listen m = RWST $ \ r s -> do + ~(a, s', w) <- runRWST m r s + return ((a, w), s', w) +{-# 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 :: (Monad m) => (w -> b) -> RWST r w s m a -> RWST r w s m (a, b) +listens f m = RWST $ \ r s -> do + ~(a, s', w) <- runRWST m r s + return ((a, f w), s', w) +{-# 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 :: (Monad m) => RWST r w s m (a, w -> w) -> RWST r w s m a +pass m = RWST $ \ r s -> do + ~((a, f), s', w) <- runRWST m r s + return (a, s', f w) +{-# 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 :: (Monad m) => (w -> w) -> RWST r w s m a -> RWST r w s m a +censor f m = RWST $ \ r s -> do + ~(a, s', w) <- runRWST m r s + return (a, s', f w) +{-# INLINE censor #-} + +-- --------------------------------------------------------------------------- +-- State operations + +-- | Construct a state monad computation from a state transformer function. +state :: (Monoid w, Monad m) => (s -> (a,s)) -> RWST r w s m a +state f = RWST $ \ _ s -> let (a,s') = f s in return (a, s', mempty) +{-# INLINE state #-} + +-- | Fetch the current value of the state within the monad. +get :: (Monoid w, Monad m) => RWST r w s m s +get = RWST $ \ _ s -> return (s, s, mempty) +{-# INLINE get #-} + +-- | @'put' s@ sets the state within the monad to @s@. +put :: (Monoid w, Monad m) => s -> RWST r w s m () +put s = RWST $ \ _ _ -> return ((), s, mempty) +{-# 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 :: (Monoid w, Monad m) => (s -> s) -> RWST r w s m () +modify f = RWST $ \ _ s -> return ((), f s, mempty) +{-# INLINE modify #-} + +-- | Get a specific component of the state, using a projection function +-- supplied. +-- +-- * @'gets' f = 'liftM' f 'get'@ +gets :: (Monoid w, Monad m) => (s -> a) -> RWST r w s m a +gets f = RWST $ \ _ s -> return (f s, s, mempty) +{-# 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 :: (Monoid w) => + CallCC m (a,s,w) (b,s,w) -> CallCC (RWST r w s m) a b +liftCallCC callCC f = RWST $ \ r s -> + callCC $ \ c -> + runRWST (f (\ a -> RWST $ \ _ _ -> c (a, s, mempty))) r s +{-# INLINE liftCallCC #-} + +-- | In-situ lifting of a @callCC@ operation to the new monad. +-- This version uses the current state on entering the continuation. +liftCallCC' :: (Monoid w) => + CallCC m (a,s,w) (b,s,w) -> CallCC (RWST r w s m) a b +liftCallCC' callCC f = RWST $ \ r s -> + callCC $ \ c -> + runRWST (f (\ a -> RWST $ \ _ s' -> c (a, s', mempty))) r s +{-# 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 -> runRWST m r s `catchE` \ e -> runRWST (h e) r s +{-# INLINE liftCatch #-} |