-- |
-- Module: Language.KURE.Rewrite 
-- Copyright: (c) 2006-2008 Andy Gill
-- License: BSD3
--
-- Maintainer: Andy Gill <andygill@ku.edu>
-- Stability: unstable
-- Portability: ghc
--
-- 'Rewrite' is a synonoym for a 'Translate' with the same source and target type.
-- This module contains the defintion of Rewrite, and some aliases for some translate functions that use 
-- Rewrite rather than Translate.

module Language.KURE.Rewrite 
	( Rewrite
	, rewrite
	, runRewrite
	) where

import Language.KURE.RewriteMonad
import Language.KURE.Translate
import Data.Monoid

-- | A 'Rewrite' is a 'Translate' that shares the same source and target type. Literally, 
-- a 'Rewrite' provides the details about how to /re-write/ a specific type.

type Rewrite m dec exp = Translate m dec exp exp

-- | 'rewrite' is our primitive way of building a Rewrite,
--  where if the rewrite is successful it is automatically marked as a non-identity rewrite. 
--
-- @rewrite $ \\ _ e -> return e@ /is not/ an identity rewrite. 

rewrite :: (Monoid dec, Monad m) => (exp1 -> RewriteM m dec exp1) -> Rewrite m dec exp1
rewrite = translate

-- | 'runRewrite' executes the rewrite, returning either a failure message,
-- or a success and the new parts of the environment.


runRewrite :: (Monoid dec,Monad m) 
	   => Rewrite m dec exp
	   -> dec 
	   -> exp 
	   -> m (Either String (exp,dec))
runRewrite = runTranslate