@@ -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
@@ -22,11 +22,11 @@ module Effectful.Internal.Monad
2222 , IOE
2323 , runEff
2424
25− -- * Prim
25+ -- * Primitive
2626 , Prim
2727 , runPrim
2828
29− -- * Unlift strategies
29+ -- ** Unlift strategies
3030 , UnliftStrategy(..)
3131 , Persistence(..)
3232 , Limit(..)
@@ -34,24 +34,29 @@ module Effectful.Internal.Monad
3434 , withUnliftStrategy
3535 , withEffToIO
3636
37− -- ** Low-level unlifts
37+ --- *** Low-level helpers
3838 , seqUnliftIO
3939 , concUnliftIO
4040
4141 -- * Effects
4242
43− -- ** Dynamic dispatch
43+ -- ** Handler
4444 , EffectHandler
4545 , LocalEnv(..)
4646 , HandlerA(..)
4747 , runHandler
48+
49+ -- *** Sending operations
4850 , send
4951
50− -- ** Static dispatch
51− , DataA(..)
52+ -- ** Primitive
53+
54+ -- *** Running
5255 , runData
5356 , evalData
5457 , execData
58+
59+ -- *** Modification
5560 , getData
5661 , putData
5762 , stateData
@@ -87,16 +92,17 @@ type role Eff nominal representational
8792-- would have the following type:
8893--
8994-- @
90−-- 'Eff' '['Effectful.Reader.Reader' 'String', 'Effectful.State.Local.State' 'Bool'] 'Integer'
95+-- 'Eff' '['Effectful.Reader.Reader' 'String', 'Effectful.State.State' 'Bool'] 'Integer'
9196-- @
9297--
9398-- Normally, a concrete list of effects is not used to parameterize 'Eff'.
9499-- Instead, the '(:>)' type class is used to express constraints on the list of
95100-- effects without coupling a computation to a concrete list of effects. For
96−-- example, the above example would be expressed with the following type:
101+-- example, the above example would more commonly be expressed with the
102+-- following type:
97103--
98104-- @
99−-- ('Effectful.Reader.Reader' 'String' ':>' es, 'Effectful.State.Local.State' 'Bool' ':>' es) => 'Eff' es 'Integer'
105+-- ('Effectful.Reader.Reader' 'String' ':>' es, 'Effectful.State.State' 'Bool' ':>' es) => 'Eff' es 'Integer'
100106-- @
101107--
102108-- This abstraction allows the computation to be used in functions that may
@@ -110,12 +116,12 @@ newtype Eff (es :: [Effect]) a = Eff (Env es -> IO a)
110116-- For running computations with side effects see 'runEff'.
111117runPureEff :: Eff '[] a -> a
112118runPureEff (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).
119+ -- unsafePerformIO is safe here since IOE was not on the stack, so no IO with
120+ -- side effects was performed (unless someone sneakily introduced side effects
121+ -- with unsafeEff, but then all bets are off).
116122 --
117123 -- Moreover, internals don't allocate any resources that require explicit
118− -- cleanup actions to run.
124+ -- cleanup actions to run, so the "Dupable" part should also be just fine.
119125 unsafeDupablePerformIO $ m =<< emptyEnv
120126
121127----------------------------------------
@@ -158,7 +164,7 @@ withUnliftStrategy unlift = localData $ \_ -> DataA (IOE unlift)
158164-- constraint for accurate stack traces in case an insufficiently powerful
159165-- 'UnliftStrategy' is used and the unlifting function fails.
160166--
161−-- /Note:/ the strategy is reset to 'SeqUnlift' inside the continuation.
167+-- /Note:/ the strategy is reset to 'SeqUnlift' for new threads.
162168withEffToIO
163169 :: (HasCallStack, IOE :> es)
164170 => ((forall r. Eff es r -> IO r) -> IO a)
@@ -303,7 +309,7 @@ instance Prim :> es => PrimMonad (Eff es) where
303309 primitive = unsafeEff_ . IO
304310
305311----------------------------------------
306−-- Dynamic dispatch
312+-- Handler
307313
308314type role LocalEnv nominal nominal
309315
@@ -327,11 +333,11 @@ type EffectHandler e es
327333
328334-- | An adapter for dynamically dispatched effects.
329335--
330−-- Represents the effect handler bundled with its environment.
336+-- Represents the effect handler bundled along with its environment.
331337data HandlerA :: Effect -> Type where
332338 HandlerA :: !(Env es) -> !(EffectHandler e es) -> HandlerA e
333339
334−-- | Run a dynamically dispatched effect with the given handler.
340+-- | Run the effect with the given handler.
335341runHandler :: HandlerA e -> Eff (e : es) a -> Eff es a
336342runHandler e m = unsafeEff $ \es0 -> do
337343 size0 <- sizeEnv es0
@@ -351,17 +357,8 @@ send op = unsafeEff $ \es -> do
351357 unEff (handle (LocalEnv es) op) handlerEs
352358
353359----------------------------------------
354−-- Static dispatch
355−
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
360+-- Helpers
362361
363−-- | Run a statically dispatched effect with the given initial state and return
364−-- the final value along with the final state.
365362runData :: DataA e -> Eff (e : es) a -> Eff es (a, DataA e)
366363runData e0 m = unsafeEff $ \es0 -> do
367364 size0 <- sizeEnv es0
@@ -369,8 +366,6 @@ runData e0 m = unsafeEff $ \es0 -> do
369366 (unsafeTailEnv size0)
370367 (\es -> (,) <$> unEff m es <*> getEnv es)
371368
372−-- | Run a statically dispatched effect with the given initial state and return
373−-- the final value, discarding the final state.
374369evalData :: DataA e -> Eff (e : es) a -> Eff es a
375370evalData e m = unsafeEff $ \es0 -> do
376371 size0 <- sizeEnv es0
@@ -378,8 +373,6 @@ evalData e m = unsafeEff $ \es0 -> do
378373 (unsafeTailEnv size0)
379374 (\es -> unEff m es)
380375
381−-- | Run a statically dispatched effect with the given initial state and return
382−-- the final state, discarding the final value.
383376execData :: DataA e -> Eff (e : es) a -> Eff es (DataA e)
384377execData e0 m = unsafeEff $ \es0 -> do
385378 size0 <- sizeEnv es0
@@ -387,27 +380,21 @@ execData e0 m = unsafeEff $ \es0 -> do
387380 (unsafeTailEnv size0)
388381 (\es -> unEff m es *> getEnv es)
389382
390−-- | Fetch the current state of the effect.
391383getData :: e :> es => Eff es (DataA e)
392384getData = unsafeEff $ \es -> getEnv es
393385
394−-- | Set the current state of the effect to the given value.
395386putData :: e :> es => DataA e -> Eff es ()
396387putData e = unsafeEff $ \es -> putEnv es e
397388
398−-- | Apply the function to the current state of the effect and return a value.
399389stateData :: e :> es => (DataA e -> (a, DataA e)) -> Eff es a
400390stateData f = unsafeEff $ \es -> stateEnv es f
401391
402−-- | Apply the monadic function to the current state of the effect and return a
403−-- value.
404392stateDataM :: e :> es => (DataA e -> Eff es (a, DataA e)) -> Eff es a
405393stateDataM f = unsafeEff $ \es -> E.mask $ \release -> do
406394 (a, e) <- (\e -> release $ unEff (f e) es) =<< getEnv es
407395 putEnv es e
408396 pure a
409397
410−-- | Execute a computation with a temporarily modified state of the effect.
411398localData :: e :> es => (DataA e -> DataA e) -> Eff es a -> Eff es a
412399localData f m = unsafeEff $ \es -> do
413400 E.bracket (stateEnv es $ \e -> (e, f e))