@@ -6,7 +6,7 @@
66-- This module is intended for internal use only, and may change without warning
77-- in subsequent releases.
88module Effectful.Internal.Monad
9− ( -- * The 'Eff' monad
9+ ( -- * Monad
1010 Eff
1111 , runPureEff
1212
@@ -16,17 +16,18 @@ module Effectful.Internal.Monad
1616 , unsafeEff_
1717
1818 -- * Fail
19− , Fail(..)
19+ , Fail
20+ , runFail
2021
2122 -- * IO
2223 , IOE
2324 , runEff
2425
25− -- * Prim
26+ -- * Primitive
2627 , Prim
2728 , runPrim
2829
29− -- * Unlift strategies
30+ -- ** Unlift strategies
3031 , UnliftStrategy(..)
3132 , Persistence(..)
3233 , Limit(..)
@@ -34,88 +35,87 @@ module Effectful.Internal.Monad
3435 , withUnliftStrategy
3536 , withEffToIO
3637
37− -- ** Low-level unlifts
38− , seqUnliftIO
39− , concUnliftIO
40−
41− -- * Effects
42−
43− -- ** Dynamic dispatch
44− , EffectHandler
45− , LocalEnv(..)
46− , HandlerA(..)
47− , runHandler
48− , send
49−
50− -- ** Static dispatch
51− , DataA(..)
52− , runData
53− , evalData
54− , execData
55− , getData
56− , putData
57− , stateData
58− , stateDataM
59− , localData
38+ --- *** Low-level helpers
39+ , unsafeWithLiftMapIO
40+ , unsafeSeqUnliftEff
41+ , unsafeConcUnliftEff
42+
43+ -- * Primitive effects
44+
45+ -- ** Running
46+ , runEffect
47+ , evalEffect
48+ , execEffect
49+
50+ -- ** Modification
51+ , getEffect
52+ , putEffect
53+ , stateEffect
54+ , stateEffectM
55+ , localEffect
6056 ) where
6157
6258import Control.Applicative (liftA2)
59+import Control.Concurrent (myThreadId)
60+import Control.Exception
6361import Control.Monad.Base
6462import Control.Monad.Fix
6563import Control.Monad.IO.Class
6664import Control.Monad.IO.Unlift
6765import Control.Monad.Primitive
6866import Control.Monad.Trans.Control
67+import Data.Unique
6968import GHC.Exts (oneShot)
7069import GHC.IO (IO(..))
7170import GHC.Stack (HasCallStack)
7271import System.IO.Unsafe (unsafeDupablePerformIO)
73−import qualified Control.Exception as E
74−import qualified Control.Monad.Catch as C
72+import qualified Control.Monad.Catch as E
7573
7674import Effectful.Internal.Effect
7775import Effectful.Internal.Env
7876import Effectful.Internal.Unlift
77+import Effectful.Internal.Utils
7978
8079type role Eff nominal representational
8180
82−-- | The 'Eff' monad provides the implementation of a computation that performs
81+-- | The 'Eff' monad provides the implementation of an operation that performs
8382-- an arbitrary set of effects. In @'Eff' es a@, @es@ is a type-level list that
84−-- contains all the effects that the computation may perform. For example, a
85−-- computation that produces an 'Integer' by consuming a 'String' from the
86−-- global environment and acting upon a single mutable value of type 'Bool'
87−-- would have the following type:
83+-- contains all the effects that the operation may perform. For example, an
84+-- operation that produces an 'Integer' by consuming a 'String' from the global
85+-- environment and acting upon a single mutable cell containing a 'Bool' would
86+-- have the following type:
8887--
8988-- @
90−-- 'Eff' '['Effectful.Reader.Reader' 'String', 'Effectful.State.Local.State' 'Bool'] 'Integer'
89+-- 'Eff' '['Effectful.Reader.Reader' 'String', 'Effectful.State.State' 'Bool'] 'Integer'
9190-- @
9291--
9392-- Normally, a concrete list of effects is not used to parameterize 'Eff'.
9493-- Instead, the '(:>)' type class is used to express constraints on the list of
95−-- effects without coupling a computation to a concrete list of effects. For
96−-- example, the above example would be expressed with the following type:
94+-- effects without coupling an operation to a concrete list of effects. For
95+-- example, the above example would more commonly be expressed with the
96+-- following type:
9797--
9898-- @
99−-- ('Effectful.Reader.Reader' 'String' ':>' es, 'Effectful.State.Local.State' 'Bool' ':>' es) => 'Eff' es 'Integer'
99+-- ('Effectful.Reader.Reader' 'String' ':>' es, 'Effectful.State.State' 'Bool' ':>' es) => 'Eff' es 'Integer'
100100-- @
101101--
102−-- This abstraction allows the computation to be used in functions that may
102+-- This abstraction allows the operation to be used in functions that may
103103-- perform other effects, and it also allows the effects to be handled in any
104104-- order.
105105newtype Eff (es :: [Effect]) a = Eff (Env es -> IO a)
106106 deriving (Monoid, Semigroup)
107107
108−-- | Run a pure 'Eff' computation.
108+-- | Run a pure 'Eff' operation.
109109--
110−-- For running computations with side effects see 'runEff'.
110+-- For running operations with side effects see 'runEff'.
111111runPureEff :: Eff '[] a -> a
112112runPureEff (Eff m) =
113− -- unsafeDupablePerformIO is safe here since IOE was not on the stack, so no
114− -- IO with side effects was performed (unless someone sneakily introduced side
115− -- effects with unsafeEff, but then all bets are off).
113+ -- unsafePerformIO is safe here since IOE was not on the stack, so no IO with
114+ -- side effects was performed (unless someone sneakily introduced side effects
115+ -- with unsafeEff, but then all bets are off).
116116 --
117117 -- Moreover, internals don't allocate any resources that require explicit
118− -- cleanup actions to run.
118+ -- cleanup actions to run, so the "Dupable" part should also be just fine.
119119 unsafeDupablePerformIO $ m =<< emptyEnv
120120
121121----------------------------------------
@@ -126,70 +126,62 @@ unEff :: Eff es a -> Env es -> IO a
126126unEff (Eff m) = m
127127
128128-- | Access the underlying 'IO' monad along with the environment.
129−--
130−-- This function is __unsafe__ because it can be used to introduce arbitrary
131−-- 'IO' actions into pure 'Eff' computations.
132129unsafeEff :: (Env es -> IO a) -> Eff es a
133130unsafeEff m = Eff (oneShot m)
134131
135132-- | Access the underlying 'IO' monad.
136−--
137−-- This function is __unsafe__ because it can be used to introduce arbitrary
138−-- 'IO' actions into pure 'Eff' computations.
139133unsafeEff_ :: IO a -> Eff es a
140134unsafeEff_ m = unsafeEff $ \_ -> m
141135
142−----------------------------------------
143−-- Unlifting IO
144−
145−-- | Get the current 'UnliftStrategy'.
146−unliftStrategy :: IOE :> es => Eff es UnliftStrategy
147−unliftStrategy = do
148− DataA (IOE unlift) <- getData
149− pure unlift
150−
151−-- | Locally override the 'UnliftStrategy' with the given value.
152−withUnliftStrategy :: IOE :> es => UnliftStrategy -> Eff es a -> Eff es a
153−withUnliftStrategy unlift = localData $ \_ -> DataA (IOE unlift)
154−
155−-- | Create an unlifting function with the current 'UnliftStrategy'.
136+-- | Utility for lifting 'IO' operations of type
156137--
157−-- This function is equivalent to 'withRunInIO', but has a 'HasCallStack'
158−-- constraint for accurate stack traces in case an insufficiently powerful
159−-- 'UnliftStrategy' is used and the unlifting function fails.
138+-- @'IO' a -> 'IO' b@
160139--
161−-- /Note:/ the strategy is reset to 'SeqUnlift' inside the continuation.
162−withEffToIO
163− :: (HasCallStack, IOE :> es)
164− => ((forall r. Eff es r -> IO r) -> IO a)
165− -- ^ Continuation with the unlifting function in scope.
166− -> Eff es a
167−withEffToIO f = unliftStrategy >>= \case
168− SeqUnlift -> unsafeEff $ \es -> seqUnliftIO es f
169− ConcUnlift p b -> withUnliftStrategy SeqUnlift $ do
170− unsafeEff $ \es -> concUnliftIO es p b f
140+-- to
141+--
142+-- @forall localEs. 'Eff' localEs a -> 'Eff' localEs b@
143+--
144+-- /Note:/ the 'IO' operation must not run its argument in a separate thread,
145+-- attempting to do so will result in a runtime error.
146+unsafeWithLiftMapIO
147+ :: HasCallStack
148+ => ((forall a b localEs. (IO a -> IO b) -> Eff localEs a -> Eff localEs b) -> Eff es r)
149+ -> Eff es r
150+unsafeWithLiftMapIO k = k $ \mapIO m -> unsafeEff $ \es -> do
151+ unsafeSeqUnliftEff es $ \unlift -> mapIO $ unlift m
171152
172−-- | Create an unlifting function with the 'SeqUnlift' strategy.
173−seqUnliftIO
153+-- | Lower 'Eff' operations into 'IO' ('SeqUnlift').
154+unsafeSeqUnliftEff
174155 :: HasCallStack
175156 => Env es
176− -- ^ The environment.
177157 -> ((forall r. Eff es r -> IO r) -> IO a)
178− -- ^ Continuation with the unlifting function in scope.
179158 -> IO a
180−seqUnliftIO es k = seqUnlift k es unEff
181−
182−-- | Create an unlifting function with the 'ConcUnlift' strategy.
183−concUnliftIO
159+unsafeSeqUnliftEff es k = do
160+ tid0 <- myThreadId
161+ k $ \m -> do
162+ tid <- myThreadId
163+ if tid `eqThreadId` tid0
164+ then unEff m es
165+ else error
166+ $ "If you want to use the unlifting function to run Eff operations "
167+ ++ "in multiple threads, have a look at UnliftStrategy (ConcUnlift)."
168+
169+-- | Lower 'Eff' operations into 'IO' ('ConcUnlift').
170+unsafeConcUnliftEff
184171 :: HasCallStack
185172 => Env es
186− -- ^ The environment.
187173 -> Persistence
188174 -> Limit
189175 -> ((forall r. Eff es r -> IO r) -> IO a)
190− -- ^ Continuation with the unlifting function in scope.
191176 -> IO a
192−concUnliftIO es persistence limit k = concUnlift persistence limit k es unEff
177+unsafeConcUnliftEff es Ephemeral (Limited uses) k =
178+ unsafeEphemeralConcUnliftIO uses k es unEff
179+unsafeConcUnliftEff es Ephemeral Unlimited k =
180+ unsafeEphemeralConcUnliftIO maxBound k es unEff
181+unsafeConcUnliftEff es Persistent (Limited threads) k =
182+ unsafePersistentConcUnliftIO False threads k es unEff
183+unsafeConcUnliftEff es Persistent Unlimited k =
184+ unsafePersistentConcUnliftIO True maxBound k es unEff
193185
194186----------------------------------------
195187-- Base
@@ -217,56 +209,84 @@ instance MonadFix (Eff es) where
217209----------------------------------------
218210-- Exception
219211
220−instance C.MonadThrow (Eff es) where
221− throwM = unsafeEff_ . E.throwIO
212+instance E.MonadThrow (Eff es) where
213+ throwM = unsafeEff_ . throwIO
222214
223−instance C.MonadCatch (Eff es) where
215+instance E.MonadCatch (Eff es) where
224216 catch m handler = unsafeEff $ \es -> do
225217 size <- sizeEnv es
226− unEff m es `E.catch` \e -> do
218+ unEff m es `catch` \e -> do
227219 checkSizeEnv size es
228220 unEff (handler e) es
229221
230−instance C.MonadMask (Eff es) where
231− mask k = unsafeEff $ \es -> E.mask $ \restore ->
222+instance E.MonadMask (Eff es) where
223+ mask k = unsafeEff $ \es -> mask $ \restore ->
232224 unEff (k $ \m -> unsafeEff $ restore . unEff m) es
233225
234− uninterruptibleMask k = unsafeEff $ \es -> E.uninterruptibleMask $ \restore ->
226+ uninterruptibleMask k = unsafeEff $ \es -> uninterruptibleMask $ \restore ->
235227 unEff (k $ \m -> unsafeEff $ restore . unEff m) es
236228
237− generalBracket acquire release use = unsafeEff $ \es -> E.mask $ \restore -> do
229+ generalBracket acquire release use = unsafeEff $ \es -> mask $ \restore -> do
238230 size <- sizeEnv es
239231 resource <- unEff acquire es
240− b <- restore (unEff (use resource) es) `E.catch` \e -> do
232+ b <- restore (unEff (use resource) es) `catch` \e -> do
241233 checkSizeEnv size es
242− _ <- unEff (release resource $ C.ExitCaseException e) es
243− E.throwIO e
234+ _ <- unEff (release resource $ E.ExitCaseException e) es
235+ throwIO e
244236 checkSizeEnv size es
245− c <- unEff (release resource $ C.ExitCaseSuccess b) es
237+ c <- unEff (release resource $ E.ExitCaseSuccess b) es
246238 pure (b, c)
247239
248240----------------------------------------
249241-- Fail
250242
251−-- | Provide the ability to use the 'MonadFail' instance of 'Eff'.
252−data Fail :: Effect where
253− Fail :: String -> Fail m a
243+newtype Fail :: Effect where
244+ Fail :: Unique -> Fail m r
245+
246+runFail :: Eff (Fail : es) a -> Eff es (Either String a)
247+runFail m = unsafeEff $ \es0 -> mask $ \release -> do
248+ -- A unique tag is picked so that different runFail handlers don't catch each
249+ -- other's exceptions.
250+ tag <- newUnique
251+ size0 <- sizeEnv es0
252+ es <- unsafeConsEnv (IdE (Fail tag)) noRelinker es0
253+ r <- tryFailIO tag (release $ unEff m es) `onException` unsafeTailEnv size0 es
254+ unsafeTailEnv size0 es
255+ pure r
254256
255257instance Fail :> es => MonadFail (Eff es) where
256− fail = send . Fail
258+ fail msg = do
259+ IdE (Fail tag) <- getEffect
260+ unsafeEff_ . throwIO $ FailEx tag msg
261+
262+--------------------
263+
264+data FailEx = FailEx !Unique String
265+instance Show FailEx where
266+ showsPrec p (FailEx _ msg)
267+ = ("Effectful.Internal.Monad.FailEx " ++)
268+ . showsPrec p msg
269+instance Exception FailEx
270+
271+tryFailIO :: Unique -> IO a -> IO (Either String a)
272+tryFailIO tag m =
273+ (Right <$> m) `catch` \err@(FailEx etag msg) -> do
274+ if tag == etag
275+ then pure $ Left msg
276+ else throwIO err
257277
258278----------------------------------------
259279-- IO
260280
261−-- | Run arbitrary 'IO' computations via 'MonadIO' or 'MonadUnliftIO'.
281+-- | Run arbitrary 'IO' operations via 'MonadIO' or 'MonadUnliftIO'.
262282newtype IOE :: Effect where
263283 IOE :: UnliftStrategy -> IOE m r
264284
265−-- | Run an 'Eff' computation with side effects.
285+-- | Run an 'Eff' operation with side effects.
266286--
267−-- For running pure computations see 'runPureEff'.
287+-- For running pure operations see 'runPureEff'.
268288runEff :: Eff '[IOE] a -> IO a
269−runEff m = unEff (evalData (DataA (IOE SeqUnlift)) m) =<< emptyEnv
289+runEff m = unEff (evalEffect (IdE (IOE SeqUnlift)) m) =<< emptyEnv
270290
271291instance IOE :> es => MonadIO (Eff es) where
272292 liftIO = unsafeEff_
@@ -290,126 +310,141 @@ instance IOE :> es => MonadBaseControl IO (Eff es) where
290310----------------------------------------
291311-- Primitive
292312
293−-- | Provide the ability to perform primitive state-transformer actions.
313+-- | An effect to perform primitive state-transformer actions.
294314data Prim :: Effect where
295315 Prim :: Prim m r
296316
297−-- | Run an 'Eff' computation with primitive state-transformer actions.
317+-- | Run an 'Eff' operation with primitive state-transformer actions.
298318runPrim :: IOE :> es => Eff (Prim : es) a -> Eff es a
299−runPrim = evalData (DataA Prim)
319+runPrim = evalEffect (IdE Prim)
300320
301321instance Prim :> es => PrimMonad (Eff es) where
302322 type PrimState (Eff es) = RealWorld
303323 primitive = unsafeEff_ . IO
304324
305325----------------------------------------
306−-- Dynamic dispatch
326+-- Unlift strategies
327+
328+-- | The strategy to use when unlifting 'Eff' operations via 'withRunInIO' or
329+-- the 'Effectful.Interpreter.localUnlift' family.
330+data UnliftStrategy
331+ = SeqUnlift
332+ -- ^ The fastest strategy and a default setting for 'IOE'. An attempt to call
333+ -- the unlifting function in threads distinct from its creator will result in
334+ -- a runtime error.
335+ | ConcUnlift !Persistence !Limit
336+ -- ^ A strategy that makes it possible for the unlifting function to be called
337+ -- in threads distinct from its creator. See 'Persistence' and 'Limit'
338+ -- settings for more information.
339+ deriving (Eq, Ord, Show)
340+
341+-- | Persistence setting for the 'ConcUnlift' strategy.
342+--
343+-- Different functions require different persistence strategies. Examples:
344+--
345+-- - Lifting 'pooledMapConcurrentlyN' from the @unliftio@ library requires the
346+-- 'Ephemeral' strategy as we don't want jobs to share environment changes
347+-- made by previous jobs run in the same worker thread.
348+--
349+-- - Lifting 'Control.Concurrent.forkIOWithUnmask' requires the 'Persistent'
350+-- strategy, otherwise the unmasking function would start with a fresh
351+-- environment each time it's called.
352+data Persistence
353+ = Ephemeral
354+ -- ^ Don't persist the environment between calls to the unlifting function in
355+ -- threads distinct from its creator.
356+ | Persistent
357+ -- ^ Persist the environment between calls to the unlifting function within a
358+ -- particular thread.
359+ deriving (Eq, Ord, Show)
360+
361+-- | Limit setting for the 'ConcUnlift' strategy.
362+data Limit
363+ = Limited !Int
364+ -- ^ Behavior dependent on the 'Persistence' setting.
365+ --
366+ -- For 'Ephemeral', it limits the amount of uses of the unlifting function in
367+ -- threads distinct from its creator to @N@. The unlifting function will
368+ -- create @N@ copies of the environment when called @N@ times and @K+1@ copies
369+ -- when called @K < N@ times.
370+ --
371+ -- For 'Persistent', it limits the amount of threads, distinct from the
372+ -- creator of the unlifting function, it can be called in to @N@. The amount
373+ -- of calls to the unlifting function within a particular threads is
374+ -- unlimited. The unlifting function will create @N@ copies of the environment
375+ -- when called in @N@ threads and @K+1@ copies when called in @K < N@ threads.
376+ | Unlimited
377+ -- ^ Unlimited use of the unlifting function.
378+ deriving (Eq, Ord, Show)
307379
308−type role LocalEnv nominal nominal
380+-- | Get the current 'UnliftStrategy'.
381+unliftStrategy :: IOE :> es => Eff es UnliftStrategy
382+unliftStrategy = do
383+ IdE (IOE unlift) <- getEffect
384+ pure unlift
309385
310−-- | Opaque representation of the 'Eff' environment at the point of calling the
311−-- 'send' function, i.e. right before the control is passed to the effect
312−-- handler.
386+-- | Locally override the 'UnliftStrategy' with a given value.
313387--
314−-- The second type variable represents effects of a handler and is needed for
315−-- technical reasons to guarantee soundness.
316−newtype LocalEnv (localEs :: [Effect]) (handlerEs :: [Effect]) = LocalEnv (Env localEs)
317−
318−-- | Type signature of the effect handler.
319−type EffectHandler e es
320− = forall a localEs. HasCallStack
321− => LocalEnv localEs es
322− -- ^ Capture of the local environment for handling local 'Eff' computations
323− -- when @e@ is a higher order effect.
324− -> e (Eff localEs) a
325− -- ^ The effect performed in the local environment.
326− -> Eff es a
388+-- /Note:/ the strategy is reset to 'SeqUnlift' for new threads.
389+withUnliftStrategy :: IOE :> es => UnliftStrategy -> Eff es a -> Eff es a
390+withUnliftStrategy unlift = localEffect $ \_ -> IdE (IOE unlift)
327391
328−-- | An adapter for dynamically dispatched effects.
392+-- | Create an unlifting function with the current 'UnliftStrategy'.
329393--
330−-- Represents the effect handler bundled with its environment.
331−data HandlerA :: Effect -> Type where
332− HandlerA :: !(Env es) -> !(EffectHandler e es) -> HandlerA e
333−
334−-- | Run a dynamically dispatched effect with the given handler.
335−runHandler :: HandlerA e -> Eff (e : es) a -> Eff es a
336−runHandler e m = unsafeEff $ \es0 -> do
337− size0 <- sizeEnv es0
338− E.bracket (unsafeConsEnv e relinker es0)
339− (unsafeTailEnv size0)
340− (\es -> unEff m es)
341− where
342− relinker :: Relinker HandlerA e
343− relinker = Relinker $ \relink (HandlerA handlerEs handle) -> do
344− newHandlerEs <- relink handlerEs
345− pure $ HandlerA newHandlerEs handle
346−
347−-- | Send an operation of the given effect to its handler for execution.
348−send :: (HasCallStack, e :> es) => e (Eff es) a -> Eff es a
349−send op = unsafeEff $ \es -> do
350− HandlerA handlerEs handle <- getEnv es
351− unEff (handle (LocalEnv es) op) handlerEs
394+-- This function is equivalent to 'withRunInIO', but has a 'HasCallStack'
395+-- constraint for accurate stack traces in case an insufficiently powerful
396+-- 'UnliftStrategy' is used and the unlifting function fails.
397+withEffToIO
398+ :: (HasCallStack, IOE :> es)
399+ => ((forall r. Eff es r -> IO r) -> IO a)
400+ -- ^ Continuation with the unlifting function in scope.
401+ -> Eff es a
402+withEffToIO f = unliftStrategy >>= \case
403+ SeqUnlift -> unsafeEff $ \es -> unsafeSeqUnliftEff es f
404+ ConcUnlift p b -> withUnliftStrategy SeqUnlift $ do
405+ unsafeEff $ \es -> unsafeConcUnliftEff es p b f
352406
353407----------------------------------------
354−-- Static dispatch
408+-- Helpers
355409
356−-- | An adapter for statically dispatched effects.
357−--
358−-- Represents an arbitrary data type with the appropriate number of phantom type
359−-- parameters.
360−newtype DataA :: Effect -> Type where
361− DataA :: (forall m r. e m r) -> DataA e
362−
363−-- | Run a statically dispatched effect with the given initial state and return
364−-- the final value along with the final state.
365−runData :: DataA e -> Eff (e : es) a -> Eff es (a, DataA e)
366−runData e0 m = unsafeEff $ \es0 -> do
410+runEffect :: handler e -> Eff (e : es) a -> Eff es (a, handler e)
411+runEffect e0 m = unsafeEff $ \es0 -> do
367412 size0 <- sizeEnv es0
368− E.bracket (unsafeConsEnv e0 noRelinker es0)
369− (unsafeTailEnv size0)
370− (\es -> (,) <$> unEff m es <*> getEnv es)
371−
372−-- | Run a statically dispatched effect with the given initial state and return
373−-- the final value, discarding the final state.
374−evalData :: DataA e -> Eff (e : es) a -> Eff es a
375−evalData e m = unsafeEff $ \es0 -> do
413+ bracket (unsafeConsEnv e0 noRelinker es0)
414+ (unsafeTailEnv size0)
415+ (\es -> (,) <$> unEff m es <*> getEnv es)
416+
417+evalEffect :: handler e -> Eff (e : es) a -> Eff es a
418+evalEffect e m = unsafeEff $ \es0 -> do
376419 size0 <- sizeEnv es0
377− E.bracket (unsafeConsEnv e noRelinker es0)
378− (unsafeTailEnv size0)
379− (\es -> unEff m es)
380−
381−-- | Run a statically dispatched effect with the given initial state and return
382−-- the final state, discarding the final value.
383−execData :: DataA e -> Eff (e : es) a -> Eff es (DataA e)
384−execData e0 m = unsafeEff $ \es0 -> do
420+ bracket (unsafeConsEnv e noRelinker es0)
421+ (unsafeTailEnv size0)
422+ (\es -> unEff m es)
423+
424+execEffect :: handler e -> Eff (e : es) a -> Eff es (handler e)
425+execEffect e0 m = unsafeEff $ \es0 -> do
385426 size0 <- sizeEnv es0
386− E.bracket (unsafeConsEnv e0 noRelinker es0)
387− (unsafeTailEnv size0)
388− (\es -> unEff m es *> getEnv es)
389−
390−-- | Fetch the current state of the effect.
391−getData :: e :> es => Eff es (DataA e)
392−getData = unsafeEff $ \es -> getEnv es
393−
394−-- | Set the current state of the effect to the given value.
395−putData :: e :> es => DataA e -> Eff es ()
396−putData e = unsafeEff $ \es -> putEnv es e
397−
398−-- | Apply the function to the current state of the effect and return a value.
399−stateData :: e :> es => (DataA e -> (a, DataA e)) -> Eff es a
400−stateData f = unsafeEff $ \es -> stateEnv es f
401−
402−-- | Apply the monadic function to the current state of the effect and return a
403−-- value.
404−stateDataM :: e :> es => (DataA e -> Eff es (a, DataA e)) -> Eff es a
405−stateDataM f = unsafeEff $ \es -> E.mask $ \release -> do
427+ bracket (unsafeConsEnv e0 noRelinker es0)
428+ (unsafeTailEnv size0)
429+ (\es -> unEff m es *> getEnv es)
430+
431+getEffect :: e :> es => Eff es (handler e)
432+getEffect = unsafeEff $ \es -> getEnv es
433+
434+putEffect :: e :> es => handler e -> Eff es ()
435+putEffect e = unsafeEff $ \es -> putEnv es e
436+
437+stateEffect :: e :> es => (handler e -> (a, handler e)) -> Eff es a
438+stateEffect f = unsafeEff $ \es -> stateEnv es f
439+
440+stateEffectM :: e :> es => (handler e -> Eff es (a, handler e)) -> Eff es a
441+stateEffectM f = unsafeEff $ \es -> mask $ \release -> do
406442 (a, e) <- (\e -> release $ unEff (f e) es) =<< getEnv es
407443 putEnv es e
408444 pure a
409445
410−-- | Execute a computation with a temporarily modified state of the effect.
411−localData :: e :> es => (DataA e -> DataA e) -> Eff es a -> Eff es a
412−localData f m = unsafeEff $ \es -> do
413− E.bracket (stateEnv es $ \e -> (e, f e))
414− (\e -> putEnv es e)
415− (\_ -> unEff m es)
446+localEffect :: e :> es => (handler e -> handler e) -> Eff es a -> Eff es a
447+localEffect f m = unsafeEff $ \es -> do
448+ bracket (stateEnv es $ \e -> (e, f e))
449+ (\e -> putEnv es e)
450+ (\_ -> unEff m es)