Transformer.hs

{-# OPTIONS_GHC -fglasgow-exts #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  Control.Arrow.Transformer
-- Copyright   :  (c) Ross Paterson 2003
-- License     :  BSD-style (see the LICENSE file in the distribution)
--
-- Maintainer  :  ross@soi.city.ac.uk
-- Stability   :  experimental
-- Portability :  non-portable (multi-parameter type classes)
--
-- Arrow transformers, for making new arrow types out of old ones.

module Control.Arrow.Transformer (
		ArrowTransformer(..)
	) where

import Control.Arrow

-- | Construct a new arrow from an existing one.
class (Arrow a, Arrow (f a)) => ArrowTransformer f a where

	-- | A transformation of arrows, preserving 'arr', '>>>' and 'first'.
	--
	-- Typical usage in arrow notation:
	--
	-- >	proc p -> ...
	-- >		(|lift cmd|)

	lift :: a b c -> f a b c