{-# LANGUAGE CPP #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE KindSignatures #-}
-- | The 'StT' type family.
module Control.Monad.Trans.Lift.StT (StT) where
import qualified Control.Monad.Trans.Except as E
import qualified Control.Monad.Trans.Identity as I
import qualified Control.Monad.Trans.List as L
import qualified Control.Monad.Trans.Maybe as M
import qualified Control.Monad.Trans.Reader as R
import qualified Control.Monad.Trans.RWS.Lazy as RWS.Lazy
import qualified Control.Monad.Trans.RWS.Strict as RWS.Strict
import qualified Control.Monad.Trans.RWS.CPS as RWS.CPS
import qualified Control.Monad.Trans.State.Lazy as S.Lazy
import qualified Control.Monad.Trans.State.Strict as S.Strict
import qualified Control.Monad.Trans.Writer.Lazy as W.Lazy
import qualified Control.Monad.Trans.Writer.Strict as W.Strict
import qualified Control.Monad.Trans.Writer.CPS as W.CPS
#if MIN_VERSION_transformers(0,5,3)
import qualified Control.Monad.Trans.Accum as Acc
#endif
-- | Internal state of a monad transformer.
-- Same as @StT@ from the @monad-control@ package.
type family StT (t :: (* -> *) -> (* -> *)) (a :: *) :: *
type instance StT (E.ExceptT e) a = Either e a
type instance StT I.IdentityT a = a
type instance StT L.ListT a = [a]
type instance StT M.MaybeT a = Maybe a
type instance StT (R.ReaderT r) a = a
type instance StT (RWS.Lazy.RWST r w s) a = (a, s, w)
type instance StT (RWS.Strict.RWST r w s) a = (a, s, w)
type instance StT (RWS.CPS.RWST r w s) a = (a, s, w)
type instance StT (S.Lazy.StateT s) a = (a, s)
type instance StT (S.Strict.StateT s) a = (a, s)
type instance StT (W.Lazy.WriterT w) a = (a, w)
type instance StT (W.Strict.WriterT w) a = (a, w)
type instance StT (W.CPS.WriterT w) a = (a, w)
#if MIN_VERSION_transformers(0,5,3)
type instance StT (Acc.AccumT w) a = (a, w)
#endif