transformers-compat-0.5.1.2: src/Control/Monad/Trans/Instances.hs
{-# LANGUAGE CPP #-}
#ifndef HASKELL98
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE EmptyDataDecls #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
# if __GLASGOW_HASKELL__ >= 702
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE Trustworthy #-}
# endif
# if __GLASGOW_HASKELL__ >= 706
{-# LANGUAGE PolyKinds #-}
# endif
# if __GLASGOW_HASKELL__ >= 708
{-# LANGUAGE DataKinds #-}
# endif
#endif
{-# OPTIONS_GHC -fno-warn-deprecations #-}
-----------------------------------------------------------------------------
-- |
-- Module : Control.Monad.Trans.Instances
-- Copyright : (C) 2012-16 Edward Kmett
-- License : BSD-style (see the file LICENSE)
-- Maintainer : Edward Kmett <ekmett@gmail.com>
-- Stability : provisional
-- Portability : portable
--
-- Backports orphan instances which are not provided by other modules in
-- @transformers-compat@.
----------------------------------------------------------------------------
module Control.Monad.Trans.Instances () where
#ifndef MIN_VERSION_base
#define MIN_VERSION_base(a,b,c) 1
#endif
#ifndef MIN_VERSION_transformers
#define MIN_VERSION_transformers(a,b,c) 1
#endif
import Control.Applicative.Backwards (Backwards(..))
import Control.Applicative.Lift (Lift(..))
import Control.Monad.IO.Class (MonadIO)
import Control.Monad.Trans.Class (MonadTrans)
import Control.Monad.Trans.Cont (ContT(..))
import Control.Monad.Trans.Error (ErrorT(..))
import Control.Monad.Trans.Except ()
import Control.Monad.Trans.Identity (IdentityT(..))
import Control.Monad.Trans.List (ListT(..))
import Control.Monad.Trans.Maybe (MaybeT(..))
import qualified Control.Monad.Trans.RWS.Lazy as Lazy (RWST(..))
import qualified Control.Monad.Trans.RWS.Strict as Strict (RWST(..))
import Control.Monad.Trans.Reader (ReaderT(..))
import qualified Control.Monad.Trans.State.Lazy as Lazy (StateT(..))
import qualified Control.Monad.Trans.State.Strict as Strict (StateT(..))
import qualified Control.Monad.Trans.Writer.Lazy as Lazy (WriterT(..))
import qualified Control.Monad.Trans.Writer.Strict as Strict (WriterT(..))
import Data.Functor.Classes
import Data.Functor.Compose (Compose(..))
import Data.Functor.Constant (Constant(..))
import Data.Functor.Identity (Identity(..))
import Data.Functor.Product (Product(..))
import Data.Functor.Reverse (Reverse(..))
import Data.Functor.Sum ()
import Control.Applicative
import Control.Monad (MonadPlus(..))
import Control.Monad.Fix (MonadFix(..))
import Data.Foldable (Foldable(..))
import Data.Maybe (fromMaybe)
import Data.Monoid (Monoid(..))
import Data.Traversable (Traversable(..))
#if MIN_VERSION_base(4,4,0)
import Control.Monad.Zip (MonadZip(..))
#endif
#if MIN_VERSION_base(4,8,0)
import Data.Bifunctor (Bifunctor(..))
#endif
#ifndef HASKELL98
import Data.Data (Data)
import Data.Typeable
# if __GLASGOW_HASKELL__ >= 702
import GHC.Generics
# endif
#endif
#if !(MIN_VERSION_transformers(0,3,0))
-- Foldable/Traversable instances
instance (Foldable f) => Foldable (ErrorT e f) where
foldMap f (ErrorT a) = foldMap (either (const mempty) f) a
instance (Traversable f) => Traversable (ErrorT e f) where
traverse f (ErrorT a) =
ErrorT <$> traverse (either (pure . Left) (fmap Right . f)) a
instance (Foldable f) => Foldable (IdentityT f) where
foldMap f (IdentityT a) = foldMap f a
instance (Traversable f) => Traversable (IdentityT f) where
traverse f (IdentityT a) = IdentityT <$> traverse f a
instance (Foldable f) => Foldable (ListT f) where
foldMap f (ListT a) = foldMap (foldMap f) a
instance (Traversable f) => Traversable (ListT f) where
traverse f (ListT a) = ListT <$> traverse (traverse f) a
instance (Foldable f) => Foldable (MaybeT f) where
foldMap f (MaybeT a) = foldMap (foldMap f) a
instance (Traversable f) => Traversable (MaybeT f) where
traverse f (MaybeT a) = MaybeT <$> traverse (traverse f) a
instance (Foldable f) => Foldable (Lazy.WriterT w f) where
foldMap f = foldMap (f . fst) . Lazy.runWriterT
instance (Traversable f) => Traversable (Lazy.WriterT w f) where
traverse f = fmap Lazy.WriterT . traverse f' . Lazy.runWriterT where
f' (a, b) = fmap (\ c -> (c, b)) (f a)
instance (Foldable f) => Foldable (Strict.WriterT w f) where
foldMap f = foldMap (f . fst) . Strict.runWriterT
instance (Traversable f) => Traversable (Strict.WriterT w f) where
traverse f = fmap Strict.WriterT . traverse f' . Strict.runWriterT where
f' (a, b) = fmap (\ c -> (c, b)) (f a)
-- MonadFix instances for IdentityT and MaybeT
instance (MonadFix m) => MonadFix (IdentityT m) where
mfix f = IdentityT (mfix (runIdentityT . f))
instance (MonadFix m) => MonadFix (MaybeT m) where
mfix f = MaybeT (mfix (runMaybeT . f . fromMaybe bomb))
where bomb = error "mfix (MaybeT): inner computation returned Nothing"
# if !(MIN_VERSION_base(4,9,0))
-- Monad instances for Product
instance (Monad f, Monad g) => Monad (Product f g) where
return x = Pair (return x) (return x)
Pair m n >>= f = Pair (m >>= fstP . f) (n >>= sndP . f)
where
fstP (Pair a _) = a
sndP (Pair _ b) = b
instance (MonadPlus f, MonadPlus g) => MonadPlus (Product f g) where
mzero = Pair mzero mzero
Pair x1 y1 `mplus` Pair x2 y2 = Pair (x1 `mplus` x2) (y1 `mplus` y2)
instance (MonadFix f, MonadFix g) => MonadFix (Product f g) where
mfix f = Pair (mfix (fstP . f)) (mfix (sndP . f))
where
fstP (Pair a _) = a
sndP (Pair _ b) = b
# endif
#endif
#if !(MIN_VERSION_transformers(0,4,0))
-- Alternative IO instance
# if !(MIN_VERSION_base(4,9,0))
-- The version bounds of transformers prior to 0.4.0.0 should prevent this
-- instance from being compiled on base-4.8.0.0 and later, but we'll put
-- a check here just to be safe.
instance Alternative IO where
empty = mzero
(<|>) = mplus
# endif
#endif
#if MIN_VERSION_transformers(0,4,0) && !(MIN_VERSION_transformers(0,4,3))
-- transformers-0.4-specific Eq1, Ord1, Read1, and Show1 instances for Const
instance (Eq a) => Eq1 (Const a) where
eq1 (Const x) (Const y) = x == y
instance (Ord a) => Ord1 (Const a) where
compare1 (Const x) (Const y) = compare x y
instance (Read a) => Read1 (Const a) where
readsPrec1 = readsData $ readsUnary "Const" Const
instance (Show a) => Show1 (Const a) where
showsPrec1 d (Const x) = showsUnary "Const" d x
#endif
#if !(MIN_VERSION_transformers(0,5,0))
-- Monoid Constant instance
instance (Monoid a) => Monoid (Constant a b) where
mempty = Constant mempty
Constant x `mappend` Constant y = Constant (x `mappend` y)
-- MonadZip instances
# if MIN_VERSION_base(4,4,0)
instance (MonadZip m) => MonadZip (IdentityT m) where
mzipWith f (IdentityT a) (IdentityT b) = IdentityT (mzipWith f a b)
instance (MonadZip m) => MonadZip (ListT m) where
mzipWith f (ListT a) (ListT b) = ListT $ mzipWith (zipWith f) a b
instance (MonadZip m) => MonadZip (MaybeT m) where
mzipWith f (MaybeT a) (MaybeT b) = MaybeT $ mzipWith (liftA2 f) a b
instance (MonadZip m) => MonadZip (ReaderT r m) where
mzipWith f (ReaderT m) (ReaderT n) = ReaderT $ \ a ->
mzipWith f (m a) (n a)
instance (Monoid w, MonadZip m) => MonadZip (Lazy.WriterT w m) where
mzipWith f (Lazy.WriterT x) (Lazy.WriterT y) = Lazy.WriterT $
mzipWith (\ ~(a, w) ~(b, w') -> (f a b, w `mappend` w')) x y
instance (Monoid w, MonadZip m) => MonadZip (Strict.WriterT w m) where
mzipWith f (Strict.WriterT x) (Strict.WriterT y) = Strict.WriterT $
mzipWith (\ (a, w) (b, w') -> (f a b, w `mappend` w')) x y
# if !(MIN_VERSION_base(4,8,0))
instance MonadZip Identity where
mzipWith f (Identity x) (Identity y) = Identity (f x y)
munzip (Identity (a, b)) = (Identity a, Identity b)
# endif
# if !(MIN_VERSION_base(4,9,0))
instance (MonadZip f, MonadZip g) => MonadZip (Product f g) where
mzipWith f (Pair x1 y1) (Pair x2 y2) = Pair (mzipWith f x1 x2) (mzipWith f y1 y2)
# endif
# endif
# if MIN_VERSION_base(4,8,0)
-- Bifunctor Constant instance
instance Bifunctor Constant where
first f (Constant x) = Constant (f x)
second _ (Constant x) = Constant x
# else
-- Monoid Identity instance
instance (Monoid a) => Monoid (Identity a) where
mempty = Identity mempty
mappend (Identity x) (Identity y) = Identity (mappend x y)
# endif
# ifndef HASKELL98
-- Typeable instances
# if __GLASGOW_HASKELL__ >= 708 && __GLASGOW_HASKELL__ < 710
deriving instance Typeable Backwards
deriving instance Typeable Constant
deriving instance Typeable ContT
deriving instance Typeable ErrorT
deriving instance Typeable IdentityT
deriving instance Typeable Lift
deriving instance Typeable ListT
deriving instance Typeable MaybeT
deriving instance Typeable MonadTrans
deriving instance Typeable Lazy.RWST
deriving instance Typeable Strict.RWST
deriving instance Typeable ReaderT
deriving instance Typeable Reverse
deriving instance Typeable Lazy.StateT
deriving instance Typeable Strict.StateT
# if !(MIN_VERSION_base(4,9,0))
deriving instance Typeable Compose
deriving instance Typeable MonadIO
deriving instance Typeable Product
# endif
# endif
-- Identity instances
# if !(MIN_VERSION_base(4,8,0))
deriving instance Typeable1 Identity
deriving instance Data a => Data (Identity a)
# if __GLASGOW_HASKELL__ >= 702
instance Generic (Identity a) where
type Rep (Identity a) = D1 MDIdentity (C1 MCIdentity (S1 MSIdentity (Rec0 a)))
from (Identity x) = M1 (M1 (M1 (K1 x)))
to (M1 (M1 (M1 (K1 x)))) = Identity x
instance Generic1 Identity where
type Rep1 Identity = D1 MDIdentity (C1 MCIdentity (S1 MSIdentity Par1))
from1 (Identity x) = M1 (M1 (M1 (Par1 x)))
to1 (M1 (M1 (M1 x))) = Identity (unPar1 x)
data MDIdentity
data MCIdentity
data MSIdentity
instance Datatype MDIdentity where
datatypeName _ = "Identity"
moduleName _ = "Data.Functor.Identity"
# if __GLASGOW_HASKELL__ >= 708
isNewtype _ = True
# endif
instance Constructor MCIdentity where
conName _ = "Identity"
conIsRecord _ = True
instance Selector MSIdentity where
selName _ = "runIdentity"
# endif
# if __GLASGOW_HASKELL__ >= 708
deriving instance Typeable 'Identity
# endif
# endif
# if !(MIN_VERSION_base(4,9,0))
# if __GLASGOW_HASKELL__ >= 702
-- Generic(1) instances for Compose
instance Generic (Compose f g a) where
type Rep (Compose f g a) =
D1 MDCompose
(C1 MCCompose
(S1 MSCompose (Rec0 (f (g a)))))
from (Compose x) = M1 (M1 (M1 (K1 x)))
to (M1 (M1 (M1 (K1 x)))) = Compose x
instance Functor f => Generic1 (Compose f g) where
type Rep1 (Compose f g) =
D1 MDCompose
(C1 MCCompose
(S1 MSCompose (f :.: Rec1 g)))
from1 (Compose x) = M1 (M1 (M1 (Comp1 (fmap Rec1 x))))
to1 (M1 (M1 (M1 x))) = Compose (fmap unRec1 (unComp1 x))
data MDCompose
data MCCompose
data MSCompose
instance Datatype MDCompose where
datatypeName _ = "Compose"
moduleName _ = "Data.Functor.Compose"
# if __GLASGOW_HASKELL__ >= 708
isNewtype _ = True
# endif
instance Constructor MCCompose where
conName _ = "Compose"
conIsRecord _ = True
instance Selector MSCompose where
selName _ = "getCompose"
-- Generic(1) instances for Product
instance Generic (Product f g a) where
type Rep (Product f g a) =
D1 MDProduct
(C1 MCPair
(S1 NoSelector (Rec0 (f a)) :*: S1 NoSelector (Rec0 (g a))))
from (Pair f g) = M1 (M1 (M1 (K1 f) :*: M1 (K1 g)))
to (M1 (M1 (M1 (K1 f) :*: M1 (K1 g)))) = Pair f g
instance Generic1 (Product f g) where
type Rep1 (Product f g) =
D1 MDProduct
(C1 MCPair
(S1 NoSelector (Rec1 f) :*: S1 NoSelector (Rec1 g)))
from1 (Pair f g) = M1 (M1 (M1 (Rec1 f) :*: M1 (Rec1 g)))
to1 (M1 (M1 (M1 f :*: M1 g))) = Pair (unRec1 f) (unRec1 g)
data MDProduct
data MCPair
instance Datatype MDProduct where
datatypeName _ = "Product"
moduleName _ = "Data.Functor.Product"
instance Constructor MCPair where
conName _ = "Pair"
# endif
# if __GLASGOW_HASKELL__ >= 708
-- Data instances for Compose and Product
deriving instance (Data (f (g a)), Typeable f, Typeable g, Typeable a)
=> Data (Compose (f :: * -> *) (g :: * -> *) (a :: *))
deriving instance (Data (f a), Data (g a), Typeable f, Typeable g, Typeable a)
=> Data (Product (f :: * -> *) (g :: * -> *) (a :: *))
# endif
# endif
# endif
#endif