gen_Show_binds,
gen_Data_binds,
gen_Typeable_binds,
- gen_Functor_binds, functorLikeTraverse, deepSubtypesContaining,
+ gen_Functor_binds,
+ FFoldType(..), functorLikeTraverse,
+ deepSubtypesContaining, foldDataConArgs,
gen_Foldable_binds,
gen_Traversable_binds,
genAuxBind
import TysPrim
import TysWiredIn
import Type
+import Var( TyVar )
import TypeRep
import VarSet
import State
\begin{code}
gen_Functor_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
gen_Functor_binds loc tycon
- = (listToBag [fmap_bind], [])
+ = (unitBag fmap_bind, [])
where
data_cons = tyConDataCons tycon
- arg = last (tyConTyVars tycon) -- argument to derive for, 'a in the above description
fmap_bind = L loc $ mkFunBind (L loc fmap_RDR) (map fmap_eqn data_cons)
fmap_eqn con = evalState (match_for_con [f_Pat] con parts) bs_RDRs
- where parts = map derive_fmap_type (dataConOrigArgTys con)
-
- derive_fmap_type :: Type -> LHsExpr RdrName -> State [RdrName] (LHsExpr RdrName)
- derive_fmap_type = functorLikeTraverse
- (\ x -> return x) -- fmap f x = x
- (\ x -> return (nlHsApp f_Expr x)) -- fmap f x = f x
- (panic "contravariant")
- (\g h x -> mkSimpleLam (\b -> h =<< (nlHsApp x `fmap` g b))) -- fmap f x = \b -> h (x (g b))
- (mkSimpleTupleCase match_for_con) -- fmap f x = case x of (a1,a2,..) -> (g1 a1,g2 a2,..)
- (\_ g x -> do gg <- mkSimpleLam g
- return $ nlHsApps fmap_RDR [gg,x]) -- fmap f x = fmap g x
- (panic "in other argument")
- (\_ g x -> g x)
- arg
+ where
+ parts = foldDataConArgs ft_fmap con
+
+ ft_fmap :: FFoldType (LHsExpr RdrName -> State [RdrName] (LHsExpr RdrName))
+ -- Tricky higher order type; I can't say I fully understand this code :-(
+ ft_fmap = FT { ft_triv = \x -> return x -- fmap f x = x
+ , ft_var = \x -> return (nlHsApp f_Expr x) -- fmap f x = f x
+ , ft_fun = \g h x -> mkSimpleLam (\b -> h =<< (nlHsApp x `fmap` g b))
+ -- fmap f x = \b -> h (x (g b))
+ , ft_tup = mkSimpleTupleCase match_for_con -- fmap f x = case x of (a1,a2,..) -> (g1 a1,g2 a2,..)
+ , ft_ty_app = \_ g x -> do gg <- mkSimpleLam g -- fmap f x = fmap g x
+ return $ nlHsApps fmap_RDR [gg,x]
+ , ft_forall = \_ g x -> g x
+ , ft_bad_app = panic "in other argument"
+ , ft_co_var = panic "contravariant" }
match_for_con = mkSimpleConMatch $
\con_name xsM -> do xs <- sequence xsM
\begin{code}
-- Generic traversal for Functor deriving
-functorLikeTraverse :: a -- ^ Case: does not contain variable
- -> a -- ^ Case: the variable itself
- -> a -- ^ Case: the variable itself, contravariantly
- -> (a -> a -> a) -- ^ Case: function type
- -> (Boxity -> [a] -> a) -- ^ Case: tuple type
- -> (Type -> a -> a) -- ^ Case: type app, variable only in last argument
- -> a -- ^ Case: type app, variable other than in last argument
- -> (TcTyVar -> a -> a) -- ^ Case: forall type
- -> TcTyVar -- ^ Variable to look for
- -> Type -- ^ Type to process
- -> a
-functorLikeTraverse caseTrivial caseVar caseCoVar caseFun caseTuple caseTyApp caseWrongArg caseForAll var ty
- = fst (go False ty)
+data FFoldType a -- Describes how to fold over a Type in a functor like way
+ = FT { ft_triv :: a -- Does not contain variable
+ , ft_var :: a -- The variable itself
+ , ft_co_var :: a -- The variable itself, contravariantly
+ , ft_fun :: a -> a -> a -- Function type
+ , ft_tup :: Boxity -> [a] -> a -- Tuple type
+ , ft_ty_app :: Type -> a -> a -- Type app, variable only in last argument
+ , ft_bad_app :: a -- Type app, variable other than in last argument
+ , ft_forall :: TcTyVar -> a -> a -- Forall type
+ }
+
+functorLikeTraverse :: TyVar -- ^ Variable to look for
+ -> FFoldType a -- ^ How to fold
+ -> Type -- ^ Type to process
+ -> a
+functorLikeTraverse var (FT { ft_triv = caseTrivial, ft_var = caseVar
+ , ft_co_var = caseCoVar, ft_fun = caseFun
+ , ft_tup = caseTuple, ft_ty_app = caseTyApp
+ , ft_bad_app = caseWrongArg, ft_forall = caseForAll })
+ ty
+ = fst (go False ty)
where -- go returns (result of type a, does type contain var)
go co ty | Just ty' <- coreView ty = go co ty'
go co (TyVarTy v) | v == var = (if co then caseCoVar else caseVar,True)
-- Return all syntactic subterms of ty that contain var somewhere
-- These are the things that should appear in instance constraints
-deepSubtypesContaining :: TcTyVar -> TcType -> [TcType]
-deepSubtypesContaining = functorLikeTraverse
- []
- []
- (panic "contravariant")
- (\x y -> x ++ y) -- function
- (\_ xs -> concat xs) -- tuple
- (\ty x -> ty : x) -- tyapp
- (panic "in other argument")
- (\v x -> filter (not . (v `elemVarSet`) . tyVarsOfType) x) -- forall v
-
+deepSubtypesContaining :: TyVar -> Type -> [TcType]
+deepSubtypesContaining tv
+ = functorLikeTraverse tv
+ (FT { ft_triv = []
+ , ft_var = []
+ , ft_fun = (++), ft_tup = \_ xs -> concat xs
+ , ft_ty_app = (:)
+ , ft_bad_app = panic "in other argument"
+ , ft_co_var = panic "contravariant"
+ , ft_forall = \v xs -> filterOut ((v `elemVarSet`) . tyVarsOfType) xs })
+
+
+foldDataConArgs :: FFoldType a -> DataCon -> [a]
+-- Fold over the arguments of the datacon
+foldDataConArgs ft con
+ = map (functorLikeTraverse tv ft) (dataConOrigArgTys con)
+ where
+ tv = last (dataConUnivTyVars con)
+ -- Argument to derive for, 'a in the above description
+ -- The validity checks have ensured that con is
+ -- a vanilla data constructor
-- Make a HsLam using a fresh variable from a State monad
mkSimpleLam :: (LHsExpr id -> State [id] (LHsExpr id)) -> State [id] (LHsExpr id)
+-- (mkSimpleLam fn) returns (\x. fn(x))
mkSimpleLam lam = do
(n:names) <- get
put names
\begin{code}
gen_Foldable_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
gen_Foldable_binds loc tycon
- = (listToBag [foldr_bind], [])
+ = (unitBag foldr_bind, [])
where
data_cons = tyConDataCons tycon
- arg = last (tyConTyVars tycon) -- argument to derive for, 'a in the above description
foldr_bind = L loc $ mkFunBind (L loc foldr_RDR) (map foldr_eqn data_cons)
foldr_eqn con = evalState (match_for_con z_Expr [f_Pat,z_Pat] con parts) bs_RDRs
- where parts = map derive_foldr_type (dataConOrigArgTys con)
-
- derive_foldr_type :: Type -> LHsExpr RdrName -> LHsExpr RdrName -> State [RdrName] (LHsExpr RdrName)
- derive_foldr_type = functorLikeTraverse
- (\ _ z -> return z) -- foldr f z x = z
- (\ x z -> return (nlHsApps f_RDR [x,z])) -- foldr f z x = f x z
- (panic "function")
- (panic "function")
- (\b gs x z -> mkSimpleTupleCase (match_for_con z) b gs x)
- (\_ g x z -> do gg <- mkSimpleLam2 g -- foldr f z x = foldr (\xx zz -> g xx zz) z x
- return $ nlHsApps foldable_foldr_RDR [gg,z,x])
- (panic "in other argument")
- (\_ g x z -> g x z)
- arg
+ where
+ parts = foldDataConArgs ft_foldr con
+
+ ft_foldr :: FFoldType (LHsExpr RdrName -> LHsExpr RdrName -> State [RdrName] (LHsExpr RdrName))
+ ft_foldr = FT { ft_triv = \_ z -> return z -- foldr f z x = z
+ , ft_var = \x z -> return (nlHsApps f_RDR [x,z]) -- foldr f z x = f x z
+ , ft_tup = \b gs x z -> mkSimpleTupleCase (match_for_con z) b gs x
+ , ft_ty_app = \_ g x z -> do gg <- mkSimpleLam2 g -- foldr f z x = foldr (\xx zz -> g xx zz) z x
+ return $ nlHsApps foldable_foldr_RDR [gg,z,x]
+ , ft_forall = \_ g x z -> g x z
+ , ft_co_var = panic "covariant"
+ , ft_fun = panic "function"
+ , ft_bad_app = panic "in other argument" }
match_for_con z = mkSimpleConMatch (\_con_name -> foldrM ($) z) -- g1 v1 (g2 v2 (.. z))
\end{code}
\begin{code}
gen_Traversable_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds)
gen_Traversable_binds loc tycon
- = (listToBag [traverse_bind], [])
+ = (unitBag traverse_bind, [])
where
data_cons = tyConDataCons tycon
- arg = last (tyConTyVars tycon) -- argument to derive for, 'a in the above description
traverse_bind = L loc $ mkFunBind (L loc traverse_RDR) (map traverse_eqn data_cons)
traverse_eqn con = evalState (match_for_con [f_Pat] con parts) bs_RDRs
- where parts = map derive_travese_type (dataConOrigArgTys con)
-
- derive_travese_type :: Type -> LHsExpr RdrName -> State [RdrName] (LHsExpr RdrName)
- derive_travese_type = functorLikeTraverse
- (\ x -> return (nlHsApps pure_RDR [x])) -- traverse f x = pure x
- (\ x -> return (nlHsApps f_RDR [x])) -- travese f x = f x
- (panic "function")
- (panic "function")
- (mkSimpleTupleCase match_for_con) -- travese f x z = case x of (a1,a2,..) -> (,,) <$> g1 a1 <*> g2 a2 <*> ..
- (\_ g x -> do gg <- mkSimpleLam g -- travese f x = travese (\xx -> g xx) x
- return $ nlHsApps traverse_RDR [gg,x])
- (panic "in other argument")
- (\_ g x -> g x)
- arg
+ where
+ parts = foldDataConArgs ft_trav con
+
+
+ ft_trav :: FFoldType (LHsExpr RdrName -> State [RdrName] (LHsExpr RdrName))
+ ft_trav = FT { ft_triv = \x -> return (nlHsApps pure_RDR [x]) -- traverse f x = pure x
+ , ft_var = \x -> return (nlHsApps f_RDR [x]) -- travese f x = f x
+ , ft_tup = mkSimpleTupleCase match_for_con -- travese f x z = case x of (a1,a2,..) ->
+ -- (,,) <$> g1 a1 <*> g2 a2 <*> ..
+ , ft_ty_app = \_ g x -> do gg <- mkSimpleLam g -- travese f x = travese (\xx -> g xx) x
+ return $ nlHsApps traverse_RDR [gg,x]
+ , ft_forall = \_ g x -> g x
+ , ft_co_var = panic "covariant"
+ , ft_fun = panic "function"
+ , ft_bad_app = panic "in other argument" }
match_for_con = mkSimpleConMatch $
\con_name xsM -> do xs <- sequence xsM
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