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{-# LANGUAGE TypeFamilies, MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances #-}
{-# LANGUAGE KindSignatures #-}
{-# OPTIONS_GHC -fno-warn-redundant-constraints -fno-warn-missing-methods #-}
module T10753 where
import Data.Kind (Type)
class MonadState s m | m -> s where
get :: m s
newtype StateT s m a = StateT { runStateT :: s -> m (a,s) }
instance (Monad m) => Monad (StateT s m) where
instance (Functor m, Monad m) => Applicative (StateT s m) where
instance (Functor m) => Functor (StateT s m) where
instance (Monad m) => MonadState s (StateT s m) where
class HasConns (m :: Type -> Type) where
type Conn m
foo :: (Monad m) => StateT (Conn m) m ()
foo =
do _ <- get
return ()
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