module Data.Geniplate(universeBi, universeBiT, transformBi, transformBiT) where
import Control.Exception(assert)
import Control.Monad.State.Strict
import Data.Maybe
import Language.Haskell.TH
import Language.Haskell.TH.Syntax hiding (lift)
universeBi :: Name -> Q Exp
universeBi = universeBiT []
universeBiT :: [TypeQ] -> Name -> Q Exp
universeBiT stops name = do
(_tvs, from, tos) <- getNameType name
let to = unList tos
(ds, f) <- uniBiQ stops from to
x <- newName "_x"
let e = LamE [VarP x] $ LetE ds $ AppE (AppE f (VarE x)) (ListE [])
return e
type U = StateT (Map Type Dec, Map Type Bool) Q
uniBiQ :: [TypeQ] -> Type -> Type -> Q ([Dec], Exp)
uniBiQ stops from ato = do
ss <- sequence stops
to <- expandSyn ato
(f, (m, _)) <- runStateT (uniBi from to) (mEmpty, mFromList $ zip ss (repeat False))
return (mElems m, f)
uniBi :: Type -> Type -> U Exp
uniBi afrom to = do
(m, c) <- get
from <- lift $ expandSyn afrom
case mLookup from m of
Just (FunD n _) -> return $ VarE n
_ -> do
f <- lift $ newName "_f"
cs <- if from == to then
lift $ fmap unFunD [d| f _x _r = _x : _r |]
else do
b <- contains to from
if b then do
put (mInsert from (FunD f [Clause [] (NormalB $ TupE []) []]) m, c)
uniBiCase from to
else
lift $ fmap unFunD [d| f _ _r = _r |]
let d = FunD f cs
modify $ \ (m', c') -> (mInsert from d m', c')
return $ VarE f
contains :: Type -> Type -> U Bool
contains to afrom = do
(m, c) <- get
from <- lift $ expandSyn afrom
case mLookup from c of
Just b -> return b
Nothing -> do
if from == to then
return True
else do
let (con, ts) = splitTypeApp from
put (m, mInsert from False c)
b <- case con of
ConT n -> containsCon n to ts
TupleT _ -> fmap or $ mapM (contains to) ts
ArrowT -> return False
ListT -> contains to (head ts)
t -> genError $ "contains: unexpected type: " ++ pprint from ++ " (" ++ show t ++ ")"
modify $ \ (m', c') -> (m', mInsert from b c')
return b
containsCon :: Name -> Type -> [Type] -> U Bool
containsCon con to ts = do
(tvs, cons) <- lift $ getTyConInfo con
let conCon (NormalC _ xs) = fmap or $ mapM (field . snd) xs
conCon (InfixC x1 _ x2) = fmap or $ mapM field [snd x1, snd x2]
conCon (RecC _ xs) = fmap or $ mapM field [ t | (_,_,t) <- xs ]
conCon c = genError $ "containsCon: " ++ show c
s = mkSubst tvs ts
field t = contains to (subst s t)
fmap or $ mapM conCon cons
unFunD :: [Dec] -> [Clause]
unFunD [FunD _ cs] = cs
unFunD _ = genError $ "unFunD"
uniBiCase :: Type -> Type -> U [Clause]
uniBiCase from to = do
let (con, ts) = splitTypeApp from
case con of
ConT n -> uniBiCon n ts to
TupleT _ -> uniBiTuple ts to
ListT -> uniBiList (head ts) to
t -> genError $ "uniBiCase: unexpected type: " ++ pprint from ++ " (" ++ show t ++ ")"
uniBiList :: Type -> Type -> U [Clause]
uniBiList t to = do
uni <- uniBi t to
rec <- uniBi (AppT ListT t) to
lift $ fmap unFunD [d| f [] _r = _r; f (_x:_xs) _r = $(return uni) _x ($(return rec) _xs _r) |]
uniBiTuple :: [Type] -> Type -> U [Clause]
uniBiTuple ts to = fmap (:[]) $ mkArm to [] TupP ts
uniBiCon :: Name -> [Type] -> Type -> U [Clause]
uniBiCon con ts to = do
(tvs, cons) <- lift $ getTyConInfo con
let genArm (NormalC c xs) = arm (ConP c) xs
genArm (InfixC x1 c x2) = arm (\ [p1, p2] -> InfixP p1 c p2) [x1, x2]
genArm (RecC c xs) = arm (ConP c) [ (b,t) | (_,b,t) <- xs ]
genArm c = genError $ "uniBiCon: " ++ show c
s = mkSubst tvs ts
arm c xs = mkArm to s c $ map snd xs
if null cons then
lift $ fmap unFunD [d| f _ _r = _r |]
else
mapM genArm cons
mkArm :: Type -> Subst -> ([Pat] -> Pat) -> [Type] -> U Clause
mkArm to s c ts = do
r <- lift $ newName "_r"
vs <- mapM (const $ lift $ newName "_x") ts
let sub v t = do
let t' = subst s t
uni <- uniBi t' to
return $ AppE (AppE uni (VarE v))
es <- zipWithM sub vs ts
let body = foldr ($) (VarE r) es
return $ Clause [c (map VarP vs), VarP r] (NormalB body) []
type Subst = [(Name, Type)]
mkSubst :: [TyVarBndr] -> [Type] -> Subst
mkSubst vs ts =
let vs' = map un vs
un (PlainTV v) = v
un (KindedTV v _) = v
in assert (length vs' == length ts) $ zip vs' ts
subst :: Subst -> Type -> Type
subst s (ForallT v c t) = ForallT v c $ subst s t
subst s t@(VarT n) = fromMaybe t $ lookup n s
subst s (AppT t1 t2) = AppT (subst s t1) (subst s t2)
subst s (SigT t k) = SigT (subst s t) k
subst _ t = t
getTyConInfo :: Name -> Q ([TyVarBndr], [Con])
getTyConInfo con = do
info <- qReify con
case info of
TyConI (DataD _ _ tvs cs _) -> return (tvs, cs)
PrimTyConI{} -> return ([], [])
i -> genError $ "unexpected TyCon: " ++ show i
getNameType :: Name -> Q ([TyVarBndr], Type, Type)
getNameType name = do
info <- qReify name
let split (ForallT tvs _ t) = (tvs ++ tvs', from, to) where (tvs', from, to) = split t
split (AppT (AppT ArrowT from) to) = ([], from, to)
split t = genError $ "Type is not an arrow: " ++ pprint t
case info of
VarI _ t _ _ -> return $ split t
_ -> genError $ "Name is not variable: " ++ pprint name
unList :: Type -> Type
unList (AppT (ConT n) t) | n == ''[] = t
unList (AppT ListT t) = t
unList t = genError $ "universeBi: Type is not a list: " ++ pprint t
splitTypeApp :: Type -> (Type, [Type])
splitTypeApp (AppT a r) = (c, rs ++ [r]) where (c, rs) = splitTypeApp a
splitTypeApp t = (t, [])
expandSyn :: Type -> Q Type
expandSyn (ForallT tvs ctx t) = liftM (ForallT tvs ctx) $ expandSyn t
expandSyn t@AppT{} = expandSynApp t []
expandSyn t@ConT{} = expandSynApp t []
expandSyn (SigT t k) = liftM (flip SigT k) $ expandSyn t
expandSyn t = return t
expandSynApp :: Type -> [Type] -> Q Type
expandSynApp (AppT t1 t2) ts = do t2' <- expandSyn t2; expandSynApp t1 (t2':ts)
expandSynApp t@(ConT n) ts = do
info <- qReify n
case info of
TyConI (TySynD _ tvs rhs) ->
let (ts', ts'') = splitAt (length tvs) ts
s = mkSubst tvs ts'
rhs' = subst s rhs
in expandSynApp rhs' ts''
_ -> return $ foldl AppT t ts
expandSynApp t ts = do t' <- expandSyn t; return $ foldl AppT t' ts
genError :: String -> a
genError msg = error $ "Data.Geniplate: " ++ msg
transformBi :: Name -> Q Exp
transformBi = transformBiT []
transformBiT :: [TypeQ] -> Name -> Q Exp
transformBiT stops name = do
(_tvs, fcn, res) <- getNameType name
f <- newName "_f"
(ds, tr) <-
case (fcn, res) of
(AppT (AppT ArrowT s) s', AppT (AppT ArrowT t) t') | s == s' && t == t' -> trBiQ stops f s t
_ -> genError $ "transformBi: malformed type: " ++ pprint (AppT (AppT ArrowT fcn) res) ++ ", should have form (S->S) -> (T->T)"
x <- newName "_x"
let e = LamE [VarP f, VarP x] $ LetE ds $ AppE tr (VarE x)
return e
trBiQ :: [TypeQ] -> Name -> Type -> Type -> Q ([Dec], Exp)
trBiQ stops f aft st = do
ss <- sequence stops
ft <- expandSyn aft
(tr, (m, _)) <- runStateT (trBi (VarE f) ft st) (mEmpty, mFromList $ zip ss (repeat False))
return (mElems m, tr)
trBi :: Exp -> Type -> Type -> U Exp
trBi f ft ast = do
(m, c) <- get
st <- lift $ expandSyn ast
case mLookup st m of
Just (FunD n _) -> return $ VarE n
_ -> do
tr <- lift $ newName "_tr"
cs <- if ft == st then
lift $ fmap unFunD [d| _f _x = $(return f) _x |]
else do
b <- contains ft st
if b then do
put (mInsert st (FunD tr [Clause [] (NormalB $ TupE []) []]) m, c)
trBiCase f ft st
else
lift $ fmap unFunD [d| f _x = _x |]
let d = FunD tr cs
modify $ \ (m', c') -> (mInsert st d m', c')
return $ VarE tr
trBiCase :: Exp -> Type -> Type -> U [Clause]
trBiCase f ft st = do
let (con, ts) = splitTypeApp st
case con of
ConT n -> trBiCon f n ft ts
TupleT _ -> trBiTuple f ft ts
ListT -> trBiList f ft (head ts)
_ -> genError $ "trBiCase: unexpected type: " ++ pprint st ++ " (" ++ show st ++ ")"
trBiList :: Exp -> Type -> Type -> U [Clause]
trBiList f ft st = do
tr <- trBi f ft st
rec <- trBi f ft (AppT ListT st)
lift $ fmap unFunD [d| _f [] = []; _f (_x:_xs) = ($(return tr) _x) : ($(return rec) _xs) |]
trBiTuple :: Exp -> Type -> [Type] -> U [Clause]
trBiTuple f ft ts = fmap (:[]) $ trMkArm f ft [] TupP TupE ts
trBiCon :: Exp -> Name -> Type -> [Type] -> U [Clause]
trBiCon f con ft ts = do
(tvs, cons) <- lift $ getTyConInfo con
let genArm (NormalC c xs) = arm (ConP c) (foldl AppE $ ConE c) xs
genArm (InfixC x1 c x2) = arm (\ [p1, p2] -> InfixP p1 c p2) (\ [e1, e2] -> InfixE (Just e1) (ConE c) (Just e2)) [x1, x2]
genArm (RecC c xs) = arm (ConP c) (foldl AppE $ ConE c) [ (b,t) | (_,b,t) <- xs ]
genArm c = genError $ "trBiCon: " ++ show c
s = mkSubst tvs ts
arm c ec xs = trMkArm f ft s c ec $ map snd xs
mapM genArm cons
trMkArm :: Exp -> Type -> Subst -> ([Pat] -> Pat) -> ([Exp] -> Exp) -> [Type] -> U Clause
trMkArm f ft s c ec ts = do
vs <- mapM (const $ lift $ newName "_x") ts
let sub v t = do
let t' = subst s t
tr <- trBi f ft t'
return $ AppE tr (VarE v)
es <- zipWithM sub vs ts
let body = ec es
return $ Clause [c (map VarP vs)] (NormalB body) []
newtype Map a b = Map [(a, b)]
mEmpty :: Map a b
mEmpty = Map []
mLookup :: (Eq a) => a -> Map a b -> Maybe b
mLookup a (Map xys) = lookup a xys
mInsert :: (Eq a) => a -> b -> Map a b -> Map a b
mInsert a b (Map xys) = Map $ (a, b) : filter ((/= a) . fst) xys
mElems :: Map a b -> [b]
mElems (Map xys) = map snd xys
mFromList :: [(a, b)] -> Map a b
mFromList xys = Map xys