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Add instances for Writer.CPS and RWS.CPS #51

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Add instances for Writer.CPS and RWS.CPS #51

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26 changes: 26 additions & 0 deletions Control/Monad/Trans/Control.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -129,6 +129,10 @@ import Control.Monad.Trans.Except ( ExceptT (ExceptT), runExceptT )
import qualified Control.Monad.Trans.RWS.Strict as Strict ( RWST (RWST), runRWST )
import qualified Control.Monad.Trans.State.Strict as Strict ( StateT (StateT), runStateT )
import qualified Control.Monad.Trans.Writer.Strict as Strict ( WriterT(WriterT), runWriterT )
#if MIN_VERSION_transformers(0,5,6)
import qualified Control.Monad.Trans.RWS.CPS as CPS ( RWST , rwsT , runRWST )
import qualified Control.Monad.Trans.Writer.CPS as CPS ( WriterT, writerT, runWriterT )
#endif

import Data.Functor.Identity ( Identity )

Expand Down Expand Up @@ -505,6 +509,24 @@ instance Monoid w => MonadTransControl (Strict.RWST r w s) where
{-# INLINABLE liftWith #-}
{-# INLINABLE restoreT #-}

#if MIN_VERSION_transformers(0,5,6)
instance Monoid w => MonadTransControl (CPS.WriterT w) where
type StT (CPS.WriterT w) a = (a, w)
liftWith f = CPS.writerT $ liftM (\x -> (x, mempty))
(f $ CPS.runWriterT)
restoreT = CPS.writerT
{-# INLINABLE liftWith #-}
{-# INLINABLE restoreT #-}

instance Monoid w => MonadTransControl (CPS.RWST r w s) where
type StT (CPS.RWST r w s) a = (a, s, w)
liftWith f =
CPS.rwsT $ \r s -> liftM (\x -> (x, s, mempty))
(f $ \t -> CPS.runRWST t r s)
restoreT mSt = CPS.rwsT $ \_ _ -> mSt
{-# INLINABLE liftWith #-}
{-# INLINABLE restoreT #-}
#endif

--------------------------------------------------------------------------------
-- MonadBaseControl type class
Expand Down Expand Up @@ -730,6 +752,10 @@ TRANS_CTX(Monoid w, Strict.WriterT w)
TRANS_CTX(Monoid w, WriterT w)
TRANS_CTX(Monoid w, Strict.RWST r w s)
TRANS_CTX(Monoid w, RWST r w s)
#if MIN_VERSION_transformers(0,5,6)
TRANS_CTX(Monoid w, CPS.WriterT w)
TRANS_CTX(Monoid w, CPS.RWST r w s)
#endif


--------------------------------------------------------------------------------
Expand Down