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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
+--
+-- * @'lift' (f k) = f' ('lift' . k) => '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
+--
+-- * @'lift' (cf m f) = liftCatch ('lift' . cf) ('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
+--
+-- * @'lift' . liftListen = liftListen . '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
+--
+-- * @'lift' . liftPass = liftPass . 'lift'@
+--
+type Pass w m a =  m (a, w -> w) -> m a