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newtype
ReaderT r (m :: Type -> Type) acan-i-haz Control.Monad.Reader.Has The reader monad transformer, which adds a read-only environment to the given monad. The return function ignores the environment, while m >>= k passes the inherited environment to both subcomputations:
ReaderT :: (r -> m a) -> ReaderT r (m :: Type -> Type) acan-i-haz Control.Monad.Reader.Has No documentation available.
-
Defines a capability type class for a reader effect. A reader provides an environment, say an initialization context or a configuration. The environment held in the reader effect can be changed (with local) within the scope of a sub-computation. Contrary to the Capability.State, such a change is local, and does not persist when the local call ends.
newtype
ReadState (m :: Type -> Type) acapability Capability.Reader Convert a state monad into a reader monad. Use this if the monad stack allows catching exceptions. See ReadStatePure.
ReadState :: m a -> ReadState (m :: Type -> Type) acapability Capability.Reader No documentation available.
newtype
ReadStatePure (m :: Type -> Type) acapability Capability.Reader Convert a pure state monad into a reader monad. Pure meaning that the monad stack does not allow catching exceptions. Otherwise, an exception occurring in the action passed to local could cause the context to remain modified outside of the call to local. E.g.
local @tag (const r') (throw MyException) `catch` \MyException -> ask @tag
returns r' instead of the previous value. Note, that no MonadIO instance is provided, as this would allow catching exceptions. See ReadState.ReadStatePure :: m a -> ReadStatePure (m :: Type -> Type) acapability Capability.Reader No documentation available.
newtype
ReadState (m :: Type -> Type) acapability Capability.Source Convert a state monad into a reader monad. Use this if the monad stack allows catching exceptions. See ReadStatePure.
ReadState :: m a -> ReadState (m :: Type -> Type) acapability Capability.Source No documentation available.
newtype
ReadStatePure (m :: Type -> Type) acapability Capability.Source Convert a pure state monad into a reader monad. Pure meaning that the monad stack does not allow catching exceptions. Otherwise, an exception occurring in the action passed to local could cause the context to remain modified outside of the call to local. E.g.
local @tag (const r') (throw MyException) `catch` \MyException -> ask @tag
returns r' instead of the previous value. Note, that no MonadIO instance is provided, as this would allow catching exceptions. See ReadState.