module Generics.MultiRec.TH
( deriveConstructors,
deriveSystem,
derivePF,
deriveIx
) where
import Generics.MultiRec.Base
import Generics.MultiRec.Constructor
import Language.Haskell.TH hiding (Fixity())
import Language.Haskell.TH.Syntax (Lift(..))
import Control.Monad
deriveConstructors :: [Name] -> Q [Dec]
deriveConstructors =
liftM concat . mapM constrInstance
deriveSystem :: Name -> [Name] -> String -> Q [Dec]
deriveSystem n ns pfn =
do
pf <- derivePF pfn ns
ix <- deriveIx n ns
return $ pf ++ ix
derivePF :: String -> [Name] -> Q [Dec]
derivePF pfn ns =
fmap (:[]) $
tySynD (mkName pfn) [] (foldr1 sum (map (pfType ns) ns))
where
sum :: Q Type -> Q Type -> Q Type
sum a b = conT ''(:+:) `appT` a `appT` b
deriveIx :: Name -> [Name] -> Q [Dec]
deriveIx s ns =
zipWithM (ixInstance s ns (length ns)) [0..] ns
constrInstance :: Name -> Q [Dec]
constrInstance n =
do
i <- reify n
let cs = case i of
TyConI (DataD _ _ _ cs _) -> cs
_ -> []
ds <- mapM mkData cs
is <- mapM mkInstance cs
return $ ds ++ is
mkData :: Con -> Q Dec
mkData (NormalC n _) =
dataD (cxt []) (mkName (nameBase n)) [] [] []
mkData (InfixC t1 n t2) =
mkData (NormalC n [t1,t2])
instance Lift Fixity where
lift Prefix = conE 'Prefix
lift (Infix a n) = conE 'Infix `appE` [| a |] `appE` [| n |]
instance Lift Associativity where
lift LeftAssociative = conE 'LeftAssociative
lift RightAssociative = conE 'RightAssociative
lift NotAssociative = conE 'NotAssociative
mkInstance :: Con -> Q Dec
mkInstance (NormalC n _) =
instanceD (cxt []) (appT (conT ''Constructor) (conT $ mkName (nameBase n)))
[funD 'conName [clause [wildP] (normalB (stringE (nameBase n))) []]]
mkInstance (InfixC t1 n t2) =
do
i <- reify n
let fi = case i of
DataConI _ _ _ f -> convertFixity f
_ -> Prefix
instanceD (cxt []) (appT (conT ''Constructor) (conT $ mkName (nameBase n)))
[funD 'conName [clause [wildP] (normalB (stringE (nameBase n))) []],
funD 'conFixity [clause [wildP] (normalB [| fi |]) []]]
where
convertFixity (Fixity n d) = Infix (convertDirection d) n
convertDirection InfixL = LeftAssociative
convertDirection InfixR = RightAssociative
convertDirection InfixN = NotAssociative
pfType :: [Name] -> Name -> Q Type
pfType ns n =
do
i <- reify n
let b = case i of
TyConI (DataD _ _ _ cs _) ->
foldr1 sum (map (pfCon ns) cs)
TyConI (TySynD t _ _) ->
conT ''K `appT` conT t
_ -> error "unknown construct"
appT (appT (conT ''(:>:)) b) (conT $ mkName (nameBase n))
where
sum :: Q Type -> Q Type -> Q Type
sum a b = conT ''(:+:) `appT` a `appT` b
pfCon :: [Name] -> Con -> Q Type
pfCon ns (NormalC n []) =
appT (appT (conT ''C) (conT $ mkName (nameBase n))) (conT ''U)
pfCon ns (NormalC n fs) =
appT (appT (conT ''C) (conT $ mkName (nameBase n))) (foldr1 prod (map (pfField ns . snd) fs))
where
prod :: Q Type -> Q Type -> Q Type
prod a b = conT ''(:*:) `appT` a `appT` b
pfCon ns (InfixC t1 n t2) =
pfCon ns (NormalC n [t1,t2])
pfField :: [Name] -> Type -> Q Type
pfField ns t@(ConT n) | n `elem` ns = conT ''I `appT` return t
pfField ns t = conT ''K `appT` return t
ixInstance :: Name -> [Name] -> Int -> Int -> Name -> Q Dec
ixInstance s ns m i n =
instanceD (cxt []) (conT ''Ix `appT` conT s `appT` conT n)
[mkFrom ns n m i, mkTo ns n m i, mkIndex n]
mkFrom :: [Name] -> Name -> Int -> Int -> Q Dec
mkFrom ns n m i =
do
let wrapE e = lrE m i (conE 'Tag `appE` e)
i <- reify n
let b = case i of
TyConI (DataD _ _ _ cs _) ->
zipWith (fromCon wrapE ns (length cs)) [0..] cs
TyConI (TySynD t _ _) ->
[clause [varP (field 0)] (normalB (wrapE $ conE 'K `appE` varE (field 0))) []]
_ -> error "unknown construct"
funD 'from_ b
mkTo :: [Name] -> Name -> Int -> Int -> Q Dec
mkTo ns n m i =
do
let wrapP p = lrP m i (conP 'Tag [p])
i <- reify n
let b = case i of
TyConI (DataD _ _ _ cs _) ->
zipWith (toCon wrapP ns (length cs)) [0..] cs
TyConI (TySynD t _ _) ->
[clause [wrapP $ conP 'K [varP (field 0)]] (normalB $ varE (field 0)) []]
_ -> error "unknown construct"
funD 'to_ b
mkIndex :: Name -> Q Dec
mkIndex n =
funD 'index [clause [] (normalB (conE (mkName (nameBase n)))) []]
fromCon :: (Q Exp -> Q Exp) -> [Name] -> Int -> Int -> Con -> Q Clause
fromCon wrap ns m i (NormalC n []) =
clause
[conP n []]
(normalB $ wrap $ lrE m i $ conE 'C `appE` (conE 'U)) []
fromCon wrap ns m i (NormalC n fs) =
clause
[conP n (map (varP . field) [0..length fs 1])]
(normalB $ wrap $ lrE m i $ conE 'C `appE` foldr1 prod (zipWith (fromField ns) [0..] (map snd fs))) []
where
prod x y = conE '(:*:) `appE` x `appE` y
fromCon wrap ns m i (InfixC t1 n t2) =
fromCon wrap ns m i (NormalC n [t1,t2])
toCon :: (Q Pat -> Q Pat) -> [Name] -> Int -> Int -> Con -> Q Clause
toCon wrap ns m i (NormalC n []) =
clause
[wrap $ lrP m i $ conP 'C [conP 'U []]]
(normalB $ conE n) []
toCon wrap ns m i (NormalC n fs) =
clause
[wrap $ lrP m i $ conP 'C [foldr1 prod (zipWith (toField ns) [0..] (map snd fs))]]
(normalB $ foldl appE (conE n) (map (varE . field) [0..length fs 1])) []
where
prod x y = conP '(:*:) [x,y]
toCon wrap ns m i (InfixC t1 n t2) =
toCon wrap ns m i (NormalC n [t1,t2])
fromField :: [Name] -> Int -> Type -> Q Exp
fromField ns nr t@(ConT n) | n `elem` ns = conE 'I `appE` (conE 'I0 `appE` varE (field nr))
fromField ns nr t = conE 'K `appE` varE (field nr)
toField :: [Name] -> Int -> Type -> Q Pat
toField ns nr t@(ConT n) | n `elem` ns = conP 'I [conP 'I0 [varP (field nr)]]
toField ns nr t = conP 'K [varP (field nr)]
field :: Int -> Name
field n = mkName $ "f" ++ show n
lrP :: Int -> Int -> (Q Pat -> Q Pat)
lrP 1 0 p = p
lrP m 0 p = conP 'L [p]
lrP m i p = conP 'R [lrP (m1) (i1) p]
lrE :: Int -> Int -> (Q Exp -> Q Exp)
lrE 1 0 e = e
lrE m 0 e = conE 'L `appE` e
lrE m i e = conE 'R `appE` lrE (m1) (i1) e