-----------------------------------------------------------------------------

-- |

-- Module      :  Control.Effect.Machinery.Default

-- Copyright   :  (c) Michael Szvetits, 2020

-- License     :  BSD3 (see the file LICENSE)

-- Maintainer  :  typedbyte@qualified.name

-- Stability   :  stable

-- Portability :  portable

--

-- This module provides default implementations for the 'MonadTrans' and

-- 'MonadTransControl' type classes.

-----------------------------------------------------------------------------

module Control.Effect.Machinery.Default (Default(..)) where

-- base

import Control.Monad.IO.Class (MonadIO)

-- monad-control

import Control.Monad.Trans.Control (MonadBaseControl, MonadTransControl, StT,
                                    liftWith, restoreT)

-- transformers

import Control.Monad.Trans.Class (MonadTrans, lift)

-- transformers-base

import Control.Monad.Base (MonadBase)

-- | This type provides default implementations for the 'MonadTrans' and

-- 'MonadTransControl' type classes. The type is intended to be targeted by the

-- @DerivingVia@ language extension when writing an effect handler newtype that

-- wraps a monad @m a@ :

--

-- @

--     newtype MyHandler m a =

--       MyHandler { runMyHandler :: m a }

--         deriving (Applicative, Functor, Monad, MonadIO)

--         deriving (MonadTrans, MonadTransControl) via 'Default'

--         deriving (MonadBase b, MonadBaseControl b)

-- @

newtype Default m a =
  Default { Default m a -> m a
runDefault :: m a }
    deriving (Functor (Default m)
a -> Default m a
Functor (Default m) =>
(forall a. a -> Default m a)
-> (forall a b. Default m (a -> b) -> Default m a -> Default m b)
-> (forall a b c.
    (a -> b -> c) -> Default m a -> Default m b -> Default m c)
-> (forall a b. Default m a -> Default m b -> Default m b)
-> (forall a b. Default m a -> Default m b -> Default m a)
-> Applicative (Default m)
Default m a -> Default m b -> Default m b
Default m a -> Default m b -> Default m a
Default m (a -> b) -> Default m a -> Default m b
(a -> b -> c) -> Default m a -> Default m b -> Default m c
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forall a b. Default m a -> Default m b -> Default m b
forall a b. Default m (a -> b) -> Default m a -> Default m b
forall a b c.
(a -> b -> c) -> Default m a -> Default m b -> Default m c
forall (f :: * -> *).
Functor f =>
(forall a. a -> f a)
-> (forall a b. f (a -> b) -> f a -> f b)
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-> (forall a b. f a -> f b -> f a)
-> Applicative f
forall (m :: * -> *). Applicative m => Functor (Default m)
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forall (m :: * -> *) a b.
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forall (m :: * -> *) a b c.
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(a -> b -> c) -> Default m a -> Default m b -> Default m c
<* :: Default m a -> Default m b -> Default m a
$c<* :: forall (m :: * -> *) a b.
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Default m a -> Default m b -> Default m a
*> :: Default m a -> Default m b -> Default m b
$c*> :: forall (m :: * -> *) a b.
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Default m a -> Default m b -> Default m b
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$cliftA2 :: forall (m :: * -> *) a b c.
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(a -> b -> c) -> Default m a -> Default m b -> Default m c
<*> :: Default m (a -> b) -> Default m a -> Default m b
$c<*> :: forall (m :: * -> *) a b.
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pure :: a -> Default m a
$cpure :: forall (m :: * -> *) a. Applicative m => a -> Default m a
$cp1Applicative :: forall (m :: * -> *). Applicative m => Functor (Default m)
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-> (forall a b. a -> Default m b -> Default m a)
-> Functor (Default m)
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a -> Default m b -> Default m a
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(a -> b) -> Default m a -> Default m b
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<$ :: a -> Default m b -> Default m a
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a -> Default m b -> Default m a
fmap :: (a -> b) -> Default m a -> Default m b
$cfmap :: forall (m :: * -> *) a b.
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(a -> b) -> Default m a -> Default m b
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a -> Default m a
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(forall a b. Default m a -> (a -> Default m b) -> Default m b)
-> (forall a b. Default m a -> Default m b -> Default m b)
-> (forall a. a -> Default m a)
-> Monad (Default m)
Default m a -> (a -> Default m b) -> Default m b
Default m a -> Default m b -> Default m b
forall a. a -> Default m a
forall a b. Default m a -> Default m b -> Default m b
forall a b. Default m a -> (a -> Default m b) -> Default m b
forall (m :: * -> *). Monad m => Applicative (Default m)
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forall (m :: * -> *) a b.
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Default m a -> Default m b -> Default m b
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forall (m :: * -> *).
Applicative m =>
(forall a b. m a -> (a -> m b) -> m b)
-> (forall a b. m a -> m b -> m b)
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$c>> :: forall (m :: * -> *) a b.
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Default m a -> Default m b -> Default m b
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Default m a -> (a -> Default m b) -> Default m b
$cp1Monad :: forall (m :: * -> *). Monad m => Applicative (Default m)
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(forall a. IO a -> Default m a) -> MonadIO (Default m)
IO a -> Default m a
forall a. IO a -> Default m a
forall (m :: * -> *).
Monad m =>
(forall a. IO a -> m a) -> MonadIO m
forall (m :: * -> *). MonadIO m => Monad (Default m)
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liftIO :: IO a -> Default m a
$cliftIO :: forall (m :: * -> *) a. MonadIO m => IO a -> Default m a
$cp1MonadIO :: forall (m :: * -> *). MonadIO m => Monad (Default m)
MonadIO)
    deriving (MonadBase b, MonadBaseControl b)

instance MonadTrans Default where
  lift :: m a -> Default m a
lift = m a -> Default m a
forall k (m :: k -> *) (a :: k). m a -> Default m a
Default
  {-# INLINE lift #-}

instance MonadTransControl Default where
  type StT Default a = a
  liftWith :: (Run Default -> m a) -> Default m a
liftWith f :: Run Default -> m a
f = m a -> Default m a
forall k (m :: k -> *) (a :: k). m a -> Default m a
Default (Run Default -> m a
f forall k (m :: k -> *) (a :: k). Default m a -> m a
Run Default
runDefault)
  {-# INLINE liftWith #-}
  restoreT :: m (StT Default a) -> Default m a
restoreT = m (StT Default a) -> Default m a
forall k (m :: k -> *) (a :: k). m a -> Default m a
Default
  {-# INLINE restoreT #-}