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Add local to MonadReader interface

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Cole Brown 2020-08-20 10:32:24 -04:00 committed by G. Allais
parent 6c3ab219bc
commit f227735cec
1 changed files with 5 additions and 0 deletions
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5
libs/base/Control/Monad/Reader.idr
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@ -9,6 +9,9 @@ interface Monad m => MonadReader stateType (m : Type -> Type) | m where
||| Get the context
ask : m stateType
||| `local f c` runs the computation `c` in an environment modified by `f`.
local : MonadReader stateType m => (stateType -> stateType) -> m a -> m a
||| The transformer on which the Reader monad is based
public export
record ReaderT (stateType : Type) (m: Type -> Type) (a: Type) where
@ -44,6 +47,8 @@ public export
implementation Monad m => MonadReader stateType (ReaderT stateType m) where
ask = MkReaderT (\st => pure st)
local f (MkReaderT action) = MkReaderT (action . f)
public export
implementation HasIO m => HasIO (ReaderT stateType m) where
liftIO f = MkReaderT (\_ => liftIO f)