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Qualify Eff.

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This commit is contained in:
Rob Rix 2018-05-06 14:16:40 -04:00
parent 0334ab0ded
commit 79e5f02108
1 changed files with 9 additions and 8 deletions
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src/Control/Effect.hs
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@ -12,10 +12,11 @@ module Control.Effect
, handleState , handleState
) where ) where
import Control.Monad.Effect import qualified Control.Monad.Effect as Eff
import Control.Monad.Effect.Reader import Control.Monad.Effect.Reader
import Control.Monad.Effect.Resumable import Control.Monad.Effect.Resumable
import Control.Monad.Effect.State import Control.Monad.Effect.State
import Prologue hiding (throwError)
throwResumable :: (Member (Resumable exc) effects, Effectful m) => exc v -> m effects v throwResumable :: (Member (Resumable exc) effects, Effectful m) => exc v -> m effects v
throwResumable = raise . throwError throwResumable = raise . throwError
@ -24,24 +25,24 @@ resume :: (Member (Resumable exc) e, Effectful m) => m e a -> (forall v . (v ->
resume m handle = raise (resumeError (lower m) (\yield -> lower . handle (raise . yield))) resume m handle = raise (resumeError (lower m) (\yield -> lower . handle (raise . yield)))
-- | Types wrapping 'Eff' actions. -- | Types wrapping 'Eff.Eff' actions.
-- --
-- Most instances of 'Effectful' will be derived using @-XGeneralizedNewtypeDeriving@, with these ultimately bottoming out on the instance for 'Eff' (for which 'raise' and 'lower' are simply the identity). Because of this, types can be nested arbitrarily deeply and still call 'raise'/'lower' just once to get at the (ultimately) underlying 'Eff'. -- Most instances of 'Effectful' will be derived using @-XGeneralizedNewtypeDeriving@, with these ultimately bottoming out on the instance for 'Eff.Eff' (for which 'raise' and 'lower' are simply the identity). Because of this, types can be nested arbitrarily deeply and still call 'raise'/'lower' just once to get at the (ultimately) underlying 'Eff.Eff'.
class Effectful m where class Effectful m where
-- | Raise an action in 'Eff' into an action in @m@. -- | Raise an action in 'Eff' into an action in @m@.
raise :: Eff effects a -> m effects a raise :: Eff.Eff effects a -> m effects a
-- | Lower an action in @m@ into an action in 'Eff'. -- | Lower an action in @m@ into an action in 'Eff'.
lower :: m effects a -> Eff effects a lower :: m effects a -> Eff.Eff effects a
instance Effectful Eff where instance Effectful Eff.Eff where
raise = id raise = id
lower = id lower = id
-- Handlers -- Handlers
-- | Raise a handler on 'Eff' to a handler on some 'Effectful' @m@. -- | Raise a handler on 'Eff.Eff' to a handler on some 'Effectful' @m@.
raiseHandler :: Effectful m => (Eff effectsA a -> Eff effectsB b) -> m effectsA a -> m effectsB b raiseHandler :: Effectful m => (Eff.Eff effectsA a -> Eff.Eff effectsB b) -> m effectsA a -> m effectsB b
raiseHandler handler = raise . handler . lower raiseHandler handler = raise . handler . lower
-- | Run a 'Reader' effect in an 'Effectful' context. -- | Run a 'Reader' effect in an 'Effectful' context.