{-# OPTIONS_GHC -fglasgow-exts -cpp -fallow-undecidable-instances #-} {-# LANGUAGE MultiParamTypeClasses, UndecidableInstances, ExistentialQuantification, Rank2Types, CPP #-} -- OPTIONS_GHC is required only for 6.4.2, not 6.6.1 {- | This module exports 'Biplate' instances for everything with 'Data' defined. Using GHC the 'Data' instances can be constructed with @deriving Data@. -} module Data.Generics.PlateData( module Data.Generics.Biplate ) where import Data.Generics.Biplate import Data.Generics.PlateInternal import Data.Generics.Str import Data.Generics import Data.Maybe import Data.List import qualified Data.IntSet as IntSet import Control.Monad.State import Data.Ratio -- | An existential box representing a type which supports SYB -- operations. data DataBox = forall a . (Typeable a, Data a) => DataBox a data Box find = Box {fromBox :: forall a . Typeable a => a -> Answer find} data Answer a = Hit {fromHit :: a} -- you just hit the element you were after (here is a cast) | Follow -- go forward, you will find something | Miss -- you failed to sink my battleship! containsMatch :: (Data start, Typeable start, Data find, Typeable find) => start -> find -> Box find #if __GLASGOW_HASKELL__ < 606 -- GHC 6.4.2 does not export typeRepKey, so we can't do the trick -- as efficiently, so we just give up and revert to always following containsMatch start find = Box query where query a = case cast a of Just y -> Hit y Nothing -> Follow #else -- GHC 6.6 does contain typeRepKey, so only follow when appropriate containsMatch start find = Box query where typeInt x = inlinePerformIO $ typeRepKey x query :: Typeable a => a -> Answer find query a = if tifind == tia then Hit (unsafeCast a) else if tia `IntSet.member` timatch then Follow else Miss where tia = typeInt $ typeOf a tifind = typeInt tfind timatch = IntSet.fromList $ map typeInt tmatch tfind = typeOf find tmatch = f [tfind] (filter ((/=) tfind . fst) $ containsList start) f want have = if null want2 then [] else want2 ++ f want2 no where want2 = map fst yes (yes,no) = partition (not . null . intersect want . snd) have containsList :: (Data a, Typeable a) => a -> [(TypeRep, [TypeRep])] containsList x = f [] [DataBox x] where f done [] = [] f done (DataBox t:odo) | tt `elem` done = f done odo | otherwise = (tt,map (\(DataBox a) -> typeOf a) xs) : f (tt:done) (xs++odo) where tt = typeOf t xs = contains t -- Ratio is strict and causes bugs with fromConstr in GHC 6.10.1 -- See bug http://hackage.haskell.org/trac/ghc/ticket/2782 evilRatio = fst $ splitTyConApp $ typeOf (undefined :: Ratio Int) contains :: (Data a, Typeable a) => a -> [DataBox] contains x | fst (splitTyConApp $ typeOf x) == evilRatio = [] | isAlgType dtyp = concatMap f ctrs | otherwise = [] where f ctr = gmapQ DataBox (asTypeOf (fromConstr ctr) x) ctrs = dataTypeConstrs dtyp dtyp = dataTypeOf x #endif instance (Data a, Typeable a) => Uniplate a where uniplate = collect_generate (fromBox answer) where answer :: Box a answer = containsMatch (undefined :: a) (undefined :: a) instance (Data a, Data b, Uniplate b, Typeable a, Typeable b) => Biplate a b where biplate = collect_generate_self (fromBox answer) where answer :: Box b answer = containsMatch (undefined :: a) (undefined :: b) newtype C x a = C {fromC :: CC x a} type CC x a = (Str x, Str x -> a) collect_generate_self :: (Data on, Data with, Typeable on, Typeable with) => (forall a . Typeable a => a -> Answer with) -> on -> CC with on collect_generate_self oracle x = res where res = case oracle x of Hit y -> (One y, \(One x) -> unsafeCast x) Follow -> collect_generate oracle x Miss -> (Zero, \_ -> x) collect_generate :: (Data on, Data with, Typeable on, Typeable with) => (forall a . Typeable a => a -> Answer with) -> on -> CC with on collect_generate oracle item = fromC $ gfoldl combine create item where -- forall a b . Data a => C with (a -> b) -> a -> C with b combine (C (c,g)) x = case collect_generate_self oracle x of (c2, g2) -> C (Two c c2, \(Two c' c2') -> g c' (g2 c2')) -- forall g . g -> C with g create x = C (Zero, \_ -> x)