module Generics.Regular.TH
( deriveConstructors,
deriveRegular,
derivePF
) where
import Generics.Regular.Base
import Generics.Regular.Constructor
import Language.Haskell.TH hiding (Fixity())
import Language.Haskell.TH.Syntax (Lift(..))
import Control.Monad
deriveConstructors :: Name -> Q [Dec]
deriveConstructors = constrInstance
deriveRegular :: Name -> String -> Q [Dec]
deriveRegular n pfn =
do
pf <- derivePF pfn n
fam <- deriveInst n
return $ pf ++ fam
derivePF :: String -> Name -> Q [Dec]
derivePF pfn n =
fmap (:[]) $
tySynD (mkName pfn) [] (pfType n)
deriveInst :: Name -> Q [Dec]
deriveInst t =
do
fcs <- mkFrom t 1 0 t
tcs <- mkTo t 1 0 t
liftM (:[]) $
instanceD (cxt []) (conT ''Regular `appT` conT t)
[funD 'from fcs, funD 'to tcs]
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
stripRecordNames :: Con -> Con
stripRecordNames (RecC n f) =
NormalC n (map (\(_, s, t) -> (s, t)) f)
stripRecordNames c = c
mkData :: Con -> Q Dec
mkData (NormalC n _) =
dataD (cxt []) (mkName (nameBase n)) [] [] []
mkData r@(RecC _ _) =
mkData (stripRecordNames r)
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 r@(RecC _ _) =
mkInstance (stripRecordNames r)
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 -> Q Type
pfType n =
do
i <- reify n
let b = case i of
TyConI (DataD _ _ _ cs _) ->
foldr1 sum (map (pfCon n) cs)
TyConI (TySynD t _ _) ->
conT ''K `appT` conT t
_ -> error "unknown construct"
b
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 r@(RecC _ _) =
pfCon ns (stripRecordNames r)
pfCon ns (InfixC t1 n t2) =
pfCon ns (NormalC n [t1,t2])
pfField :: Name -> Type -> Q Type
pfField ns t@(ConT n) | n == ns = conT ''I
pfField ns t = conT ''K `appT` return t
mkFrom :: Name -> Int -> Int -> Name -> Q [Q Clause]
mkFrom ns m i n =
do
let wrapE e = lrE m i e
i <- reify n
let dn = mkName (nameBase n)
let b = case i of
TyConI (DataD _ _ _ cs _) ->
zipWith (fromCon wrapE ns dn (length cs)) [0..] cs
TyConI (TySynD t _ _) ->
[clause [varP (field 0)] (normalB (wrapE $ conE 'K `appE` varE (field 0))) []]
_ -> error "unknown construct"
return b
mkTo :: Name -> Int -> Int -> Name -> Q [Q Clause]
mkTo ns m i n =
do
let wrapP p = lrP m i p
i <- reify n
let dn = mkName (nameBase n)
let b = case i of
TyConI (DataD _ _ _ cs _) ->
zipWith (toCon wrapP ns dn (length cs)) [0..] cs
TyConI (TySynD t _ _) ->
[clause [wrapP $ conP 'K [varP (field 0)]] (normalB $ varE (field 0)) []]
_ -> error "unknown construct"
return b
fromCon :: (Q Exp -> Q Exp) -> Name -> Name -> Int -> Int -> Con -> Q Clause
fromCon wrap ns n m i (NormalC cn []) =
clause
[conP cn []]
(normalB $ wrap $ lrE m i $ conE 'C `appE` (conE 'U)) []
fromCon wrap ns n m i (NormalC cn fs) =
clause
[conP cn (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 n m i r@(RecC _ _) =
fromCon wrap ns n m i (stripRecordNames r)
fromCon wrap ns n m i (InfixC t1 cn t2) =
fromCon wrap ns n m i (NormalC cn [t1,t2])
toCon :: (Q Pat -> Q Pat) -> Name -> Name -> Int -> Int -> Con -> Q Clause
toCon wrap ns n m i (NormalC cn []) =
clause
[wrap $ lrP m i $ conP 'C [conP 'U []]]
(normalB $ conE cn) []
toCon wrap ns n m i (NormalC cn fs) =
clause
[wrap $ lrP m i $ conP 'C [foldr1 prod (zipWith (toField ns) [0..] (map snd fs))]]
(normalB $ foldl appE (conE cn) (map (varE . field) [0..length fs 1])) []
where
prod x y = conP '(:*:) [x,y]
toCon wrap ns n m i r@(RecC _ _) =
toCon wrap ns n m i (stripRecordNames r)
toCon wrap ns n m i (InfixC t1 cn t2) =
toCon wrap ns n m i (NormalC cn [t1,t2])
fromField :: Name -> Int -> Type -> Q Exp
fromField ns nr t@(ConT n) | n == ns = conE 'I `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 == ns = conP 'I [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