d92b4a7 · effectful · git.iko.soy

src/Effectful/Internal/Env.hs+54−2

compare with master

unifiedsplit

@@ -40,8 +40,8 @@ import Effectful.Internal.Effect

40

41type role Env nominal

42

43−-- | A thread local, mutable, strict (elements are kept in weak head normal

44−-- form), extensible record indexed by data types of kind 'Effect'.

43+-- | A strict (WHNF), thread local, mutable, extensible record indexed by types

44+-- of kind 'Effect'.

45--

46-- Supports forking, i.e. introduction of local branches for encapsulation of

47-- data specific to effect interpreters.

@@ -56,6 +56,58 @@ type role Env nominal

56--

57-- - Modification of a specific element: /O(1)/.

58--

59+-- Here's an example of how the environment might look:

60+--

61+-- @

62+-- e00 - e01 - e05 - e07 (*)

63+-- | | |

64+-- | e06 e08 - e09

65+-- |

66+-- e02 - e03

67+-- |

68+-- e04

69+-- @

70+--

71+-- The point of execution is currently at (*), i.e. the mainline. Moreover,

72+-- currently:

73+--

74+-- - Mainline sees @[e00, e01, e05, e07]@.

75+--

76+-- - @e01@ is an interpreted effect, its handler sees @[e00, e02, e03]@.

77+--

78+-- - @e03@ is an interpreted effect, its handler sees @[e00, e02, e04]@.

79+--

80+-- - @e05@ is an interpreted effect, its handler sees @[e00, e01, e06]@.

81+--

82+-- - @e07@ is an interpreted effect, its handler sees @[e00, e01, e05, e08,

83+-- e09]@.

84+--

85+-- If an operation from @e01@ is invoked, the environment in the middle of

86+-- handling it might look like this:

87+--

88+-- @

89+-- e00 - e01 - e05 - e07

90+-- | | |

91+-- | e06 e08 - e09

92+-- |

93+-- e02 - e03 - e10 (*)

94+-- | |

95+-- e04 e11

96+-- |

97+-- e12

98+-- @

99+--

100+-- The point of execution is at (*), i.e. inside the handler of @e01@. The

101+-- handler needed to introduce @e10@ (which introduced @e11@, which in turn

102+-- introduced @e12@), so its local environment was temporarily extended with

103+-- it. Moreover, currently:

104+--

105+-- - Handler of @e01@ sees @[e00, e02, e03, e10]@.

106+--

107+-- - Handler of @e10@ sees @[e00, e02, e03, e11]@.

108+--

109+-- - Handler of @e11@ sees @[e00, e02, e03, e12]@.

110+--

59data Env (es :: [Effect]) = Env

111data Env (es :: [Effect]) = Env

60 { _forks :: Forks

112 { _forks :: Forks

61 , _globalRef :: IORef EnvRef

113 , _globalRef :: IORef EnvRef

src/Effectful/State.hs+1−1

@@ -23,7 +23,7 @@ module Effectful.State

23import Effectful.Internal.Effect

24import Effectful.Internal.Monad

25

26−-- | Provide access to a strict, thread local, mutable state of type @s@.

26+-- | Provide access to a strict (WHNF), thread local, mutable state of type @s@.

27newtype State s :: Effect where

28 State :: s -> State s m r

29

src/Effectful/State/MVar.hs+1−1

@@ -25,7 +25,7 @@ import Control.Concurrent.MVar

25import Effectful.Internal.Effect

26import Effectful.Internal.Monad

27

28−-- | Provide access to a strict, shareable, mutable state of type @s@.

28+-- | Provide access to a strict (WHNF), shareable, mutable state of type @s@.

29newtype State s :: Effect where

30 State :: MVar s -> State s m r

31

src/Effectful/Writer.hs+9−7

@@ -1,4 +1,4 @@

1−-- | The 'Writer' as an effect.

1+-- | The 'Writer' effect.

2module Effectful.Writer

3 ( Writer

4 , runWriter

@@ -15,7 +15,8 @@ import Effectful.Internal.Effect

15import Effectful.Internal.Env

16import Effectful.Internal.Monad

17

18−-- | Provide access to a write only value of type @w@.

18+-- | Provide access to a strict (WHNF), thread local, write only value of type

19+-- @w@.

19newtype Writer w :: Effect where

20newtype Writer w :: Effect where

20 Writer :: w -> Writer w m r

21 Writer :: w -> Writer w m r

21

22

@@ -41,11 +42,12 @@ listen

41 -> Eff es (a, w)

42 -> Eff es (a, w)

42listen m = unsafeEff $ \es -> mask $ \restore -> do

43listen m = unsafeEff $ \es -> mask $ \restore -> do

43 w0 <- unsafeStateEnv (\(IdE (Writer w)) -> (w, IdE (Writer mempty))) es

44 w0 <- unsafeStateEnv (\(IdE (Writer w)) -> (w, IdE (Writer mempty))) es

45+ a <- restore (unEff m es) `onException` merge es w0

46+ (a, ) <$> merge es w0

47+ where

48+ merge es w0 =

44− -- If an exception is thrown, restore e0 and keep parts of e1.

49+ -- If an exception is thrown, restore w0 and keep parts of w1.

45− a <- restore (unEff m es) `onException`

46− unsafeModifyEnv (\(IdE (Writer w)) -> IdE (Writer (w0 <> w))) es

47− w1 <- unsafeStateEnv (\(IdE (Writer w)) -> (w, IdE (Writer (w0 <> w)))) es

50+ unsafeStateEnv (\(IdE (Writer w1)) -> (w1, IdE (Writer (w0 <> w1)))) es

48− pure (a, w1)

49

51

50listens

52listens

51 :: (Writer w :> es, Monoid w)

53 :: (Writer w :> es, Monoid w)

src/Effectful/Writer/MVar.hs+1

@@ -15,6 +15,7 @@ import Effectful.Internal.Effect

15import Effectful.Internal.Env

16import Effectful.Internal.Monad

17

18+-- | Provide access to a strict (WHNF), shareable, write only value of type @w@.

18newtype Writer w :: Effect where

19newtype Writer w :: Effect where

19 Writer :: MVar w -> Writer w m r

20 Writer :: MVar w -> Writer w m r

20

21