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{-# LANGUAGE CPP #-} #if GLASGOW_HASKELL >= 702 {-# LANGUAGE Safe #-} #endif #if GLASGOW_HASKELL >= 706 {-# LANGUAGE PolyKinds #-} #endif

-- | -- Module : Control.Monad.Signatures -- Copyright : (c) Ross Paterson 2012 -- License : BSD-style (see the file LICENSE)

-- Maintainer : R.Paterson@city.ac.uk -- Stability : experimental -- Portability : portable

-- Signatures for monad operations that require specialized lifting. -- Each signature has a uniformity property that the lifting should satisfy.

module Control.Monad.Signatures ( CallCC, Catch, Listen, Pass ) where

-- | Signature of the @callCC@ operation, -- introduced in "Control.Monad.Trans.Cont". -- Any lifting function @liftCallCC@ should satisfy

-- * @'Control.Monad.Trans.Class.lift' (f k) = f' ('Control.Monad.Trans.Class.lift' . k) => 'Control.Monad.Trans.Class.lift' (cf f) = liftCallCC cf f'@

type CallCC m a b = ((a -> m b) -> m a) -> m a

-- | Signature of the @catchE@ operation, -- introduced in "Control.Monad.Trans.Except". -- Any lifting function @liftCatch@ should satisfy

-- * @'Control.Monad.Trans.Class.lift' (cf m f) = liftCatch ('Control.Monad.Trans.Class.lift' . cf) ('Control.Monad.Trans.Class.lift' f)@

type Catch e m a = m a -> (e -> m a) -> m a

-- | Signature of the @listen@ operation, -- introduced in "Control.Monad.Trans.Writer". -- Any lifting function @liftListen@ should satisfy

-- * @'Control.Monad.Trans.Class.lift' . liftListen = liftListen . 'Control.Monad.Trans.Class.lift'@

type Listen w m a = m a -> m (a, w)

-- | Signature of the @pass@ operation, -- introduced in "Control.Monad.Trans.Writer". -- Any lifting function @liftPass@ should satisfy

-- * @'Control.Monad.Trans.Class.lift' . liftPass = liftPass . 'Control.Monad.Trans.Class.lift'@

type Pass w m a = m (a, w -> w) -> m a