+\subsection{Typeable}
+%* *
+%************************************************************************
+
+From the data type
+
+ data T a b = ....
+
+we generate
+
+ instance (Typeable a, Typeable b) => Typeable (T a b) where
+ typeOf _ = mkTypeRep (mkTyConRep "T")
+ [typeOf (undefined::a),
+ typeOf (undefined::b)]
+
+Notice the use of lexically scoped type variables.
+
+\begin{code}
+gen_Typeable_binds :: TyCon -> RdrNameMonoBinds
+gen_Typeable_binds tycon
+ = mk_easy_FunMonoBind tycon_loc typeOf_RDR [wildPat] []
+ (mkHsApps mkTypeRep_RDR [tycon_rep, arg_reps])
+ where
+ tycon_loc = getSrcLoc tycon
+ tyvars = tyConTyVars tycon
+ tycon_rep = HsVar mkTyConRep_RDR `HsApp` HsLit (mkHsString (showSDoc (ppr tycon)))
+ arg_reps = ExplicitList placeHolderType (map mk tyvars)
+ mk tyvar = HsApp (HsVar typeOf_RDR)
+ (ExprWithTySig (HsVar undefined_RDR)
+ (HsTyVar (getRdrName tyvar)))
+\end{code}
+
+
+
+%************************************************************************
+%* *
+\subsection{Data}
+%* *
+%************************************************************************
+
+From the data type
+
+ data T a b = T1 a b | T2
+
+we generate
+
+ $cT1 = mkConstr 1 "T1" Prefix
+ $cT2 = mkConstr 2 "T2" Prefix
+ $dT = mkDataType [$con_T1, $con_T2]
+
+ instance (Data a, Data b) => Data (T a b) where
+ gfoldl k z (T1 a b) = z T `k` a `k` b
+ gfoldl k z T2 = z T2
+ -- ToDo: add gmapT,Q,M, gfoldr
+
+ fromConstr c = case conIndex c of
+ 1 -> T1 undefined undefined
+ 2 -> T2
+
+ toConstr (T1 _ _) = $cT1
+ toConstr T2 = $cT2
+
+ dataTypeOf _ = $dT
+
+\begin{code}
+gen_Data_binds :: FixityEnv
+ -> TyCon
+ -> (RdrNameMonoBinds, -- The method bindings
+ RdrNameMonoBinds) -- Auxiliary bindings
+gen_Data_binds fix_env tycon
+ = (andMonoBindList [gfoldl_bind, fromCon_bind, toCon_bind, dataTypeOf_bind],
+ -- Auxiliary definitions: the data type and constructors
+ datatype_bind `AndMonoBinds` andMonoBindList (map mk_con_bind data_cons))
+ where
+ tycon_loc = getSrcLoc tycon
+ data_cons = tyConDataCons tycon
+
+ ------------ gfoldl
+ gfoldl_bind = mk_FunMonoBind tycon_loc gfoldl_RDR (map gfoldl_eqn data_cons)
+ gfoldl_eqn con = ([VarPat k_RDR, VarPat z_RDR, mkConPat con_name as_needed],
+ foldl mk_k_app (HsVar z_RDR `HsApp` HsVar con_name) as_needed)
+ where
+ con_name :: RdrName
+ con_name = getRdrName con
+ as_needed = take (dataConSourceArity con) as_RDRs
+ mk_k_app e v = HsPar (mkHsOpApp e k_RDR (HsVar v))
+
+ ------------ fromConstr
+ fromCon_bind = mk_FunMonoBind tycon_loc fromConstr_RDR [([c_Pat], from_con_rhs)]
+ from_con_rhs = HsCase (HsVar conIndex_RDR `HsApp` c_Expr)
+ (map from_con_alt data_cons) tycon_loc
+ from_con_alt dc = mk_triv_Match (LitPat (HsInt (toInteger (dataConTag dc))))
+ (mkHsVarApps (getRdrName dc)
+ (replicate (dataConSourceArity dc) undefined_RDR))
+
+ ------------ toConstr
+ toCon_bind = mk_FunMonoBind tycon_loc toConstr_RDR (map to_con_eqn data_cons)
+ to_con_eqn dc = ([mkWildConPat dc], HsVar (mkConstrName dc))
+
+ ------------ dataTypeOf
+ dataTypeOf_bind = mk_easy_FunMonoBind tycon_loc dataTypeOf_RDR [wildPat]
+ [] (HsVar data_type_name)
+
+ ------------ $dT
+ data_type_name = mkDataTypeName tycon
+ datatype_bind = mkVarMonoBind tycon_loc data_type_name
+ (ExplicitList placeHolderType constrs)
+ constrs = [HsVar (mkConstrName con) | con <- data_cons]
+
+ ------------ $cT1 etc
+ mk_con_bind dc = mkVarMonoBind tycon_loc (mkConstrName dc)
+ (mkHsApps mkConstr_RDR (constr_args dc))
+ constr_args dc = [mkHsIntLit (toInteger (dataConTag dc)), -- Tag
+ HsLit (mkHsString (occNameUserString dc_occ)), -- String name
+ HsVar fixity] -- Fixity
+ where
+ dc_occ = getOccName dc
+ is_infix = isDataSymOcc dc_occ
+ fixity | is_infix = infix_RDR
+ | otherwise = prefix_RDR
+
+gfoldl_RDR = varQual_RDR gENERICS_Name FSLIT("gfoldl")
+fromConstr_RDR = varQual_RDR gENERICS_Name FSLIT("fromConstr")
+toConstr_RDR = varQual_RDR gENERICS_Name FSLIT("toConstr")
+dataTypeOf_RDR = varQual_RDR gENERICS_Name FSLIT("dataTypeOf")
+mkConstr_RDR = varQual_RDR gENERICS_Name FSLIT("mkConstr")
+mkDataType_RDR = varQual_RDR gENERICS_Name FSLIT("mkDataType")
+conIndex_RDR = varQual_RDR gENERICS_Name FSLIT("conIndex")
+prefix_RDR = dataQual_RDR gENERICS_Name FSLIT("Prefix")
+infix_RDR = dataQual_RDR gENERICS_Name FSLIT("Infix")
+
+mkDataTypeName :: TyCon -> RdrName -- $tT
+mkDataTypeName tc = mkRdrUnqual (mkDataTOcc (getOccName tc))
+
+mkConstrName :: DataCon -> RdrName -- $cT1
+mkConstrName con = mkRdrUnqual (mkDataCOcc (getOccName con))
+
+
+apN :: Int -> (a -> a) -> a -> a
+apN 0 k z = z
+apN n k z = apN (n-1) k (k z)
+\end{code}
+
+%************************************************************************
+%* *