module TcGenDeriv ( DerivAuxBinds, isDupAux, gen_Bounded_binds, gen_Enum_binds, gen_Eq_binds, gen_Ix_binds, gen_Ord_binds, gen_Read_binds, gen_Show_binds, gen_Data_binds, gen_Typeable_binds, gen_Functor_binds, FFoldType(..), functorLikeTraverse, deepSubtypesContaining, foldDataConArgs, gen_Foldable_binds, gen_Traversable_binds, genAuxBind ) where #include "HsVersions.h" import HsSyn import RdrName import BasicTypes import DataCon import Name import HscTypes import PrelInfo import MkCore ( eRROR_ID ) import PrelNames hiding (error_RDR) import PrimOp import SrcLoc import TyCon import TcType import TysPrim import TysWiredIn import Type import TypeRep import VarSet import Module import State import Util import MonadUtils import Outputable import FastString import Bag import Fingerprint import Constants import Data.List ( partition, intersperse )\end{code} \begin{code}
type DerivAuxBinds = [DerivAuxBind] data DerivAuxBind -- Please add these auxiliary top-level bindings = GenCon2Tag TyCon -- The con2Tag for given TyCon | GenTag2Con TyCon -- ...ditto tag2Con | GenMaxTag TyCon -- ...and maxTag -- All these generate ZERO-BASED tag operations -- I.e first constructor has tag 0 -- Scrap your boilerplate | MkDataCon DataCon -- For constructor C we get $cC :: Constr | MkTyCon TyCon -- For tycon T we get $tT :: DataType isDupAux :: DerivAuxBind -> DerivAuxBind -> Bool isDupAux (GenCon2Tag tc1) (GenCon2Tag tc2) = tc1 == tc2 isDupAux (GenTag2Con tc1) (GenTag2Con tc2) = tc1 == tc2 isDupAux (GenMaxTag tc1) (GenMaxTag tc2) = tc1 == tc2 isDupAux (MkDataCon dc1) (MkDataCon dc2) = dc1 == dc2 isDupAux (MkTyCon tc1) (MkTyCon tc2) = tc1 == tc2 isDupAux _ _ = False\end{code} %************************************************************************ %* * Eq instances %* * %************************************************************************ Here are the heuristics for the code we generate for @Eq@: \begin{itemize} \item Let's assume we have a data type with some (possibly zero) nullary data constructors and some ordinary, non-nullary ones (the rest, also possibly zero of them). Here's an example, with both \tr{N}ullary and \tr{O}rdinary data cons. \begin{verbatim} data Foo ... = N1 | N2 ... | Nn | O1 a b | O2 Int | O3 Double b b | ... \end{verbatim} \item For the ordinary constructors (if any), we emit clauses to do The Usual Thing, e.g.,: \begin{verbatim} (==) (O1 a1 b1) (O1 a2 b2) = a1 == a2 && b1 == b2 (==) (O2 a1) (O2 a2) = a1 == a2 (==) (O3 a1 b1 c1) (O3 a2 b2 c2) = a1 == a2 && b1 == b2 && c1 == c2 \end{verbatim} Note: if we're comparing unlifted things, e.g., if \tr{a1} and \tr{a2} are \tr{Float#}s, then we have to generate \begin{verbatim} case (a1 `eqFloat#` a2) of r -> r \end{verbatim} for that particular test. \item If there are any nullary constructors, we emit a catch-all clause of the form: \begin{verbatim} (==) a b = case (con2tag_Foo a) of { a# -> case (con2tag_Foo b) of { b# -> case (a# ==# b#) of { r -> r }}} \end{verbatim} If there aren't any nullary constructors, we emit a simpler catch-all: \begin{verbatim} (==) a b = False \end{verbatim} \item For the @(/=)@ method, we normally just use the default method. If the type is an enumeration type, we could/may/should? generate special code that calls @con2tag_Foo@, much like for @(==)@ shown above. \item We thought about doing this: If we're also deriving @Ord@ for this tycon, we generate: \begin{verbatim} instance ... Eq (Foo ...) where (==) a b = case (compare a b) of { _LT -> False; _EQ -> True ; _GT -> False} (/=) a b = case (compare a b) of { _LT -> True ; _EQ -> False; _GT -> True } \begin{verbatim} However, that requires that \tr{Ord
gen_Eq_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds) gen_Eq_binds loc tycon = (method_binds, aux_binds) where (nullary_cons, nonnullary_cons) | isNewTyCon tycon = ([], tyConDataCons tycon) | otherwise = partition isNullarySrcDataCon (tyConDataCons tycon) no_nullary_cons = null nullary_cons rest | no_nullary_cons = case tyConSingleDataCon_maybe tycon of Just _ -> [] Nothing -> -- if cons don't match, then False [([nlWildPat, nlWildPat], false_Expr)] | otherwise -- calc. and compare the tags = [([a_Pat, b_Pat], untag_Expr tycon [(a_RDR,ah_RDR), (b_RDR,bh_RDR)] (genOpApp (nlHsVar ah_RDR) eqInt_RDR (nlHsVar bh_RDR)))] aux_binds | no_nullary_cons = [] | otherwise = [GenCon2Tag tycon] method_binds = listToBag [eq_bind, ne_bind] eq_bind = mk_FunBind loc eq_RDR (map pats_etc nonnullary_cons ++ rest) ne_bind = mk_easy_FunBind loc ne_RDR [a_Pat, b_Pat] ( nlHsApp (nlHsVar not_RDR) (nlHsPar (nlHsVarApps eq_RDR [a_RDR, b_RDR]))) ------------------------------------------------------------------ pats_etc data_con = let con1_pat = nlConVarPat data_con_RDR as_needed con2_pat = nlConVarPat data_con_RDR bs_needed data_con_RDR = getRdrName data_con con_arity = length tys_needed as_needed = take con_arity as_RDRs bs_needed = take con_arity bs_RDRs tys_needed = dataConOrigArgTys data_con in ([con1_pat, con2_pat], nested_eq_expr tys_needed as_needed bs_needed) where nested_eq_expr [] [] [] = true_Expr nested_eq_expr tys as bs = foldl1 and_Expr (zipWith3Equal "nested_eq" nested_eq tys as bs) where nested_eq ty a b = nlHsPar (eq_Expr tycon ty (nlHsVar a) (nlHsVar b))\end{code} %************************************************************************ %* * Ord instances %* * %************************************************************************ Note [Generating Ord instances] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Suppose constructors are K1..Kn, and some are nullary. The general form we generate is: * Do case on first argument case a of K1 ... -> rhs_1 K2 ... -> rhs_2 ... Kn ... -> rhs_n _ -> nullary_rhs * To make rhs_i If i = 1, 2, n-1, n, generate a single case. rhs_2 case b of K1 {} -> LT K2 ... -> ...eq_rhs(K2)... _ -> GT Otherwise do a tag compare against the bigger range (because this is the one most likely to succeed) rhs_3 case tag b of tb -> if 3 <# tg then GT else case b of K3 ... -> ...eq_rhs(K3).... _ -> LT * To make eq_rhs(K), which knows that a = K a1 .. av b = K b1 .. bv we just want to compare (a1,b1) then (a2,b2) etc. Take care on the last field to tail-call into comparing av,bv * To make nullary_rhs generate this case con2tag a of a# -> case con2tag b of -> a# `compare` b# Several special cases: * Two or fewer nullary constructors: don't generate nullary_rhs * Be careful about unlifted comparisons. When comparing unboxed values we can't call the overloaded functions. See function unliftedOrdOp Note [Do not rely on compare] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ It's a bad idea to define only 'compare', and build the other binary comparisions on top of it; see Trac #2130, #4019. Reason: we don't want to laboriously make a three-way comparison, only to extract a binary result, something like this: (>) (I# x) (I# y) = case <# x y of True -> False False -> case ==# x y of True -> False False -> True So for sufficiently small types (few constructors, or all nullary) we generate all methods; for large ones we just use 'compare'. \begin{code}
data OrdOp = OrdCompare | OrdLT | OrdLE | OrdGE | OrdGT ------------ ordMethRdr :: OrdOp -> RdrName ordMethRdr op = case op of OrdCompare -> compare_RDR OrdLT -> lt_RDR OrdLE -> le_RDR OrdGE -> ge_RDR OrdGT -> gt_RDR ------------ ltResult :: OrdOp -> LHsExpr RdrName -- Knowing a<b, what is the result for a `op` b? ltResult OrdCompare = ltTag_Expr ltResult OrdLT = true_Expr ltResult OrdLE = true_Expr ltResult OrdGE = false_Expr ltResult OrdGT = false_Expr ------------ eqResult :: OrdOp -> LHsExpr RdrName -- Knowing a=b, what is the result for a `op` b? eqResult OrdCompare = eqTag_Expr eqResult OrdLT = false_Expr eqResult OrdLE = true_Expr eqResult OrdGE = true_Expr eqResult OrdGT = false_Expr ------------ gtResult :: OrdOp -> LHsExpr RdrName -- Knowing a>b, what is the result for a `op` b? gtResult OrdCompare = gtTag_Expr gtResult OrdLT = false_Expr gtResult OrdLE = false_Expr gtResult OrdGE = true_Expr gtResult OrdGT = true_Expr ------------ gen_Ord_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds) gen_Ord_binds loc tycon | null tycon_data_cons -- No data-cons => invoke bale-out case = (unitBag $ mk_FunBind loc compare_RDR [], []) | otherwise = (unitBag (mkOrdOp OrdCompare) `unionBags` other_ops, aux_binds) where aux_binds | single_con_type = [] | otherwise = [GenCon2Tag tycon] -- Note [Do not rely on compare] other_ops | (last_tag - first_tag) <= 2 -- 1-3 constructors || null non_nullary_cons -- Or it's an enumeration = listToBag (map mkOrdOp [OrdLT,OrdLE,OrdGE,OrdGT]) | otherwise = emptyBag get_tag con = dataConTag con - fIRST_TAG -- We want *zero-based* tags, because that's what -- con2Tag returns (generated by untag_Expr)! tycon_data_cons = tyConDataCons tycon single_con_type = isSingleton tycon_data_cons (first_con : _) = tycon_data_cons (last_con : _) = reverse tycon_data_cons first_tag = get_tag first_con last_tag = get_tag last_con (nullary_cons, non_nullary_cons) = partition isNullarySrcDataCon tycon_data_cons mkOrdOp :: OrdOp -> LHsBind RdrName -- Returns a binding op a b = ... compares a and b according to op .... mkOrdOp op = mk_easy_FunBind loc (ordMethRdr op) [a_Pat, b_Pat] (mkOrdOpRhs op) mkOrdOpRhs :: OrdOp -> LHsExpr RdrName mkOrdOpRhs op -- RHS for comparing 'a' and 'b' according to op | length nullary_cons <= 2 -- Two nullary or fewer, so use cases = nlHsCase (nlHsVar a_RDR) $ map (mkOrdOpAlt op) tycon_data_cons -- i.e. case a of { C1 x y -> case b of C1 x y -> ....compare x,y... -- C2 x -> case b of C2 x -> ....comopare x.... } | null non_nullary_cons -- All nullary, so go straight to comparing tags = mkTagCmp op | otherwise -- Mixed nullary and non-nullary = nlHsCase (nlHsVar a_RDR) $ (map (mkOrdOpAlt op) non_nullary_cons ++ [mkSimpleHsAlt nlWildPat (mkTagCmp op)]) mkOrdOpAlt :: OrdOp -> DataCon -> LMatch RdrName -- Make the alternative (Ki a1 a2 .. av -> mkOrdOpAlt op data_con = mkSimpleHsAlt (nlConVarPat data_con_RDR as_needed) (mkInnerRhs op data_con) where as_needed = take (dataConSourceArity data_con) as_RDRs data_con_RDR = getRdrName data_con mkInnerRhs op data_con | single_con_type = nlHsCase (nlHsVar b_RDR) [ mkInnerEqAlt op data_con ] | tag == first_tag = nlHsCase (nlHsVar b_RDR) [ mkInnerEqAlt op data_con , mkSimpleHsAlt nlWildPat (ltResult op) ] | tag == last_tag = nlHsCase (nlHsVar b_RDR) [ mkInnerEqAlt op data_con , mkSimpleHsAlt nlWildPat (gtResult op) ] | tag == first_tag + 1 = nlHsCase (nlHsVar b_RDR) [ mkSimpleHsAlt (nlConWildPat first_con) (gtResult op) , mkInnerEqAlt op data_con , mkSimpleHsAlt nlWildPat (ltResult op) ] | tag == last_tag - 1 = nlHsCase (nlHsVar b_RDR) [ mkSimpleHsAlt (nlConWildPat last_con) (ltResult op) , mkInnerEqAlt op data_con , mkSimpleHsAlt nlWildPat (gtResult op) ] | tag > last_tag `div` 2 -- lower range is larger = untag_Expr tycon [(b_RDR, bh_RDR)] $ nlHsIf (genOpApp (nlHsVar bh_RDR) ltInt_RDR tag_lit) (gtResult op) $ -- Definitely GT nlHsCase (nlHsVar b_RDR) [ mkInnerEqAlt op data_con , mkSimpleHsAlt nlWildPat (ltResult op) ] | otherwise -- upper range is larger = untag_Expr tycon [(b_RDR, bh_RDR)] $ nlHsIf (genOpApp (nlHsVar bh_RDR) gtInt_RDR tag_lit) (ltResult op) $ -- Definitely LT nlHsCase (nlHsVar b_RDR) [ mkInnerEqAlt op data_con , mkSimpleHsAlt nlWildPat (gtResult op) ] where tag = get_tag data_con tag_lit = noLoc (HsLit (HsIntPrim (toInteger tag))) mkInnerEqAlt :: OrdOp -> DataCon -> LMatch RdrName -- First argument 'a' known to be built with K -- Returns a case alternative Ki b1 b2 ... bv -> compare (a1,a2,...) with (b1,b2,...) mkInnerEqAlt op data_con = mkSimpleHsAlt (nlConVarPat data_con_RDR bs_needed) $ mkCompareFields tycon op (dataConOrigArgTys data_con) where data_con_RDR = getRdrName data_con bs_needed = take (dataConSourceArity data_con) bs_RDRs mkTagCmp :: OrdOp -> LHsExpr RdrName -- Both constructors known to be nullary -- genreates (case data2Tag a of a# -> case data2Tag b of b# -> a# `op` b# mkTagCmp op = untag_Expr tycon [(a_RDR, ah_RDR),(b_RDR, bh_RDR)] $ unliftedOrdOp tycon intPrimTy op ah_RDR bh_RDR mkCompareFields :: TyCon -> OrdOp -> [Type] -> LHsExpr RdrName -- Generates nested comparisons for (a1,a2...) against (b1,b2,...) -- where the ai,bi have the given types mkCompareFields tycon op tys = go tys as_RDRs bs_RDRs where go [] _ _ = eqResult op go [ty] (a:_) (b:_) | isUnLiftedType ty = unliftedOrdOp tycon ty op a b | otherwise = genOpApp (nlHsVar a) (ordMethRdr op) (nlHsVar b) go (ty:tys) (a:as) (b:bs) = mk_compare ty a b (ltResult op) (go tys as bs) (gtResult op) go _ _ _ = panic "mkCompareFields" -- (mk_compare ty a b) generates -- (case (compare a b) of { LT -> <lt>; EQ -> <eq>; GT -> <bt> }) -- but with suitable special cases for mk_compare ty a b lt eq gt | isUnLiftedType ty = unliftedCompare lt_op eq_op a_expr b_expr lt eq gt | otherwise = nlHsCase (nlHsPar (nlHsApp (nlHsApp (nlHsVar compare_RDR) a_expr) b_expr)) [mkSimpleHsAlt (nlNullaryConPat ltTag_RDR) lt, mkSimpleHsAlt (nlNullaryConPat eqTag_RDR) eq, mkSimpleHsAlt (nlNullaryConPat gtTag_RDR) gt] where a_expr = nlHsVar a b_expr = nlHsVar b (lt_op, _, eq_op, _, _) = primOrdOps "Ord" tycon ty unliftedOrdOp :: TyCon -> Type -> OrdOp -> RdrName -> RdrName -> LHsExpr RdrName unliftedOrdOp tycon ty op a b = case op of OrdCompare -> unliftedCompare lt_op eq_op a_expr b_expr ltTag_Expr eqTag_Expr gtTag_Expr OrdLT -> wrap lt_op OrdLE -> wrap le_op OrdGE -> wrap ge_op OrdGT -> wrap gt_op where (lt_op, le_op, eq_op, ge_op, gt_op) = primOrdOps "Ord" tycon ty wrap prim_op = genOpApp a_expr (primOpRdrName prim_op) b_expr a_expr = nlHsVar a b_expr = nlHsVar b unliftedCompare :: PrimOp -> PrimOp -> LHsExpr RdrName -> LHsExpr RdrName -- What to cmpare -> LHsExpr RdrName -> LHsExpr RdrName -> LHsExpr RdrName -- Three results -> LHsExpr RdrName -- Return (if a < b then lt else if a == b then eq else gt) unliftedCompare lt_op eq_op a_expr b_expr lt eq gt = nlHsIf (genOpApp a_expr (primOpRdrName lt_op) b_expr) lt $ -- Test (<) first, not (==), becuase the latter -- is true less often, so putting it first would -- mean more tests (dynamically) nlHsIf (genOpApp a_expr (primOpRdrName eq_op) b_expr) eq gt nlConWildPat :: DataCon -> LPat RdrName -- The pattern (K {}) nlConWildPat con = noLoc (ConPatIn (noLoc (getRdrName con)) (RecCon (HsRecFields { rec_flds = [] , rec_dotdot = Nothing })))\end{code} %************************************************************************ %* * Enum instances %* * %************************************************************************ @Enum@ can only be derived for enumeration types. For a type \begin{verbatim} data Foo ... = N1 | N2 | ... | Nn \end{verbatim} we use both @con2tag_Foo@ and @tag2con_Foo@ functions, as well as a @maxtag_Foo@ variable (all generated by @gen_tag_n_con_binds@). \begin{verbatim} instance ... Enum (Foo ...) where succ x = toEnum (1 + fromEnum x) pred x = toEnum (fromEnum x - 1) toEnum i = tag2con_Foo i enumFrom a = map tag2con_Foo [con2tag_Foo a .. maxtag_Foo] -- or, really... enumFrom a = case con2tag_Foo a of a# -> map tag2con_Foo (enumFromTo (I# a#) maxtag_Foo) enumFromThen a b = map tag2con_Foo [con2tag_Foo a, con2tag_Foo b .. maxtag_Foo] -- or, really... enumFromThen a b = case con2tag_Foo a of { a# -> case con2tag_Foo b of { b# -> map tag2con_Foo (enumFromThenTo (I# a#) (I# b#) maxtag_Foo) }} \end{verbatim} For @enumFromTo@ and @enumFromThenTo@, we use the default methods. \begin{code}
gen_Enum_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds) gen_Enum_binds loc tycon = (method_binds, aux_binds) where method_binds = listToBag [ succ_enum, pred_enum, to_enum, enum_from, enum_from_then, from_enum ] aux_binds = [GenCon2Tag tycon, GenTag2Con tycon, GenMaxTag tycon] occ_nm = getOccString tycon succ_enum = mk_easy_FunBind loc succ_RDR [a_Pat] $ untag_Expr tycon [(a_RDR, ah_RDR)] $ nlHsIf (nlHsApps eq_RDR [nlHsVar (maxtag_RDR tycon), nlHsVarApps intDataCon_RDR [ah_RDR]]) (illegal_Expr "succ" occ_nm "tried to take `succ' of last tag in enumeration") (nlHsApp (nlHsVar (tag2con_RDR tycon)) (nlHsApps plus_RDR [nlHsVarApps intDataCon_RDR [ah_RDR], nlHsIntLit 1])) pred_enum = mk_easy_FunBind loc pred_RDR [a_Pat] $ untag_Expr tycon [(a_RDR, ah_RDR)] $ nlHsIf (nlHsApps eq_RDR [nlHsIntLit 0, nlHsVarApps intDataCon_RDR [ah_RDR]]) (illegal_Expr "pred" occ_nm "tried to take `pred' of first tag in enumeration") (nlHsApp (nlHsVar (tag2con_RDR tycon)) (nlHsApps plus_RDR [nlHsVarApps intDataCon_RDR [ah_RDR], nlHsLit (HsInt (-1))])) to_enum = mk_easy_FunBind loc toEnum_RDR [a_Pat] $ nlHsIf (nlHsApps and_RDR [nlHsApps ge_RDR [nlHsVar a_RDR, nlHsIntLit 0], nlHsApps le_RDR [nlHsVar a_RDR, nlHsVar (maxtag_RDR tycon)]]) (nlHsVarApps (tag2con_RDR tycon) [a_RDR]) (illegal_toEnum_tag occ_nm (maxtag_RDR tycon)) enum_from = mk_easy_FunBind loc enumFrom_RDR [a_Pat] $ untag_Expr tycon [(a_RDR, ah_RDR)] $ nlHsApps map_RDR [nlHsVar (tag2con_RDR tycon), nlHsPar (enum_from_to_Expr (nlHsVarApps intDataCon_RDR [ah_RDR]) (nlHsVar (maxtag_RDR tycon)))] enum_from_then = mk_easy_FunBind loc enumFromThen_RDR [a_Pat, b_Pat] $ untag_Expr tycon [(a_RDR, ah_RDR), (b_RDR, bh_RDR)] $ nlHsApp (nlHsVarApps map_RDR [tag2con_RDR tycon]) $ nlHsPar (enum_from_then_to_Expr (nlHsVarApps intDataCon_RDR [ah_RDR]) (nlHsVarApps intDataCon_RDR [bh_RDR]) (nlHsIf (nlHsApps gt_RDR [nlHsVarApps intDataCon_RDR [ah_RDR], nlHsVarApps intDataCon_RDR [bh_RDR]]) (nlHsIntLit 0) (nlHsVar (maxtag_RDR tycon)) )) from_enum = mk_easy_FunBind loc fromEnum_RDR [a_Pat] $ untag_Expr tycon [(a_RDR, ah_RDR)] $ (nlHsVarApps intDataCon_RDR [ah_RDR])\end{code} %************************************************************************ %* * Bounded instances %* * %************************************************************************ \begin{code}
gen_Bounded_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds) gen_Bounded_binds loc tycon | isEnumerationTyCon tycon = (listToBag [ min_bound_enum, max_bound_enum ], []) | otherwise = ASSERT(isSingleton data_cons) (listToBag [ min_bound_1con, max_bound_1con ], []) where data_cons = tyConDataCons tycon ----- enum-flavored: --------------------------- min_bound_enum = mkHsVarBind loc minBound_RDR (nlHsVar data_con_1_RDR) max_bound_enum = mkHsVarBind loc maxBound_RDR (nlHsVar data_con_N_RDR) data_con_1 = head data_cons data_con_N = last data_cons data_con_1_RDR = getRdrName data_con_1 data_con_N_RDR = getRdrName data_con_N ----- single-constructor-flavored: ------------- arity = dataConSourceArity data_con_1 min_bound_1con = mkHsVarBind loc minBound_RDR $ nlHsVarApps data_con_1_RDR (nOfThem arity minBound_RDR) max_bound_1con = mkHsVarBind loc maxBound_RDR $ nlHsVarApps data_con_1_RDR (nOfThem arity maxBound_RDR)\end{code} %************************************************************************ %* * Ix instances %* * %************************************************************************ Deriving @Ix@ is only possible for enumeration types and single-constructor types. We deal with them in turn. For an enumeration type, e.g., \begin{verbatim} data Foo ... = N1 | N2 | ... | Nn \end{verbatim} things go not too differently from @Enum@: \begin{verbatim} instance ... Ix (Foo ...) where range (a, b) = map tag2con_Foo [con2tag_Foo a .. con2tag_Foo b] -- or, really... range (a, b) = case (con2tag_Foo a) of { a# -> case (con2tag_Foo b) of { b# -> map tag2con_Foo (enumFromTo (I# a#) (I# b#)) }} -- Generate code for unsafeIndex, becuase using index leads -- to lots of redundant range tests unsafeIndex c@(a, b) d = case (con2tag_Foo d -# con2tag_Foo a) of r# -> I# r# inRange (a, b) c = let p_tag = con2tag_Foo c in p_tag >= con2tag_Foo a && p_tag <= con2tag_Foo b -- or, really... inRange (a, b) c = case (con2tag_Foo a) of { a_tag -> case (con2tag_Foo b) of { b_tag -> case (con2tag_Foo c) of { c_tag -> if (c_tag >=# a_tag) then c_tag <=# b_tag else False }}} \end{verbatim} (modulo suitable case-ification to handle the unlifted tags) For a single-constructor type (NB: this includes all tuples), e.g., \begin{verbatim} data Foo ... = MkFoo a b Int Double c c \end{verbatim} we follow the scheme given in Figure~19 of the Haskell~1.2 report (p.~147). \begin{code}
gen_Ix_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds) gen_Ix_binds loc tycon | isEnumerationTyCon tycon = (enum_ixes, [GenCon2Tag tycon, GenTag2Con tycon, GenMaxTag tycon]) | otherwise = (single_con_ixes, [GenCon2Tag tycon]) where -------------------------------------------------------------- enum_ixes = listToBag [ enum_range, enum_index, enum_inRange ] enum_range = mk_easy_FunBind loc range_RDR [nlTuplePat [a_Pat, b_Pat] Boxed] $ untag_Expr tycon [(a_RDR, ah_RDR)] $ untag_Expr tycon [(b_RDR, bh_RDR)] $ nlHsApp (nlHsVarApps map_RDR [tag2con_RDR tycon]) $ nlHsPar (enum_from_to_Expr (nlHsVarApps intDataCon_RDR [ah_RDR]) (nlHsVarApps intDataCon_RDR [bh_RDR])) enum_index = mk_easy_FunBind loc unsafeIndex_RDR [noLoc (AsPat (noLoc c_RDR) (nlTuplePat [a_Pat, nlWildPat] Boxed)), d_Pat] ( untag_Expr tycon [(a_RDR, ah_RDR)] ( untag_Expr tycon [(d_RDR, dh_RDR)] ( let rhs = nlHsVarApps intDataCon_RDR [c_RDR] in nlHsCase (genOpApp (nlHsVar dh_RDR) minusInt_RDR (nlHsVar ah_RDR)) [mkSimpleHsAlt (nlVarPat c_RDR) rhs] )) ) enum_inRange = mk_easy_FunBind loc inRange_RDR [nlTuplePat [a_Pat, b_Pat] Boxed, c_Pat] $ untag_Expr tycon [(a_RDR, ah_RDR)] ( untag_Expr tycon [(b_RDR, bh_RDR)] ( untag_Expr tycon [(c_RDR, ch_RDR)] ( nlHsIf (genOpApp (nlHsVar ch_RDR) geInt_RDR (nlHsVar ah_RDR)) ( (genOpApp (nlHsVar ch_RDR) leInt_RDR (nlHsVar bh_RDR)) ) {-else-} ( false_Expr )))) -------------------------------------------------------------- single_con_ixes = listToBag [single_con_range, single_con_index, single_con_inRange] data_con = case tyConSingleDataCon_maybe tycon of -- just checking... Nothing -> panic "get_Ix_binds" Just dc -> dc con_arity = dataConSourceArity data_con data_con_RDR = getRdrName data_con as_needed = take con_arity as_RDRs bs_needed = take con_arity bs_RDRs cs_needed = take con_arity cs_RDRs con_pat xs = nlConVarPat data_con_RDR xs con_expr = nlHsVarApps data_con_RDR cs_needed -------------------------------------------------------------- single_con_range = mk_easy_FunBind loc range_RDR [nlTuplePat [con_pat as_needed, con_pat bs_needed] Boxed] $ noLoc (mkHsComp ListComp stmts con_expr) where stmts = zipWith3Equal "single_con_range" mk_qual as_needed bs_needed cs_needed mk_qual a b c = noLoc $ mkBindStmt (nlVarPat c) (nlHsApp (nlHsVar range_RDR) (mkLHsVarTuple [a,b])) ---------------- single_con_index = mk_easy_FunBind loc unsafeIndex_RDR [nlTuplePat [con_pat as_needed, con_pat bs_needed] Boxed, con_pat cs_needed] -- We need to reverse the order we consider the components in -- so that -- range (l,u) !! index (l,u) i == i -- when i is in range -- (from http://haskell.org/onlinereport/ix.html) holds. (mk_index (reverse $ zip3 as_needed bs_needed cs_needed)) where -- index (l1,u1) i1 + rangeSize (l1,u1) * (index (l2,u2) i2 + ...) mk_index [] = nlHsIntLit 0 mk_index [(l,u,i)] = mk_one l u i mk_index ((l,u,i) : rest) = genOpApp ( mk_one l u i ) plus_RDR ( genOpApp ( (nlHsApp (nlHsVar unsafeRangeSize_RDR) (mkLHsVarTuple [l,u])) ) times_RDR (mk_index rest) ) mk_one l u i = nlHsApps unsafeIndex_RDR [mkLHsVarTuple [l,u], nlHsVar i] ------------------ single_con_inRange = mk_easy_FunBind loc inRange_RDR [nlTuplePat [con_pat as_needed, con_pat bs_needed] Boxed, con_pat cs_needed] $ foldl1 and_Expr (zipWith3Equal "single_con_inRange" in_range as_needed bs_needed cs_needed) where in_range a b c = nlHsApps inRange_RDR [mkLHsVarTuple [a,b], nlHsVar c]\end{code} %************************************************************************ %* * Read instances %* * %************************************************************************ Example infix 4 %% data T = Int %% Int | T1 { f1 :: Int } | T2 T instance Read T where readPrec = parens ( prec 4 ( do x <- ReadP.step Read.readPrec Symbol "%%" <- Lex.lex y <- ReadP.step Read.readPrec return (x %% y)) +++ prec (appPrec+1) ( -- Note the "+1" part; "T2 T1 {f1=3}" should parse ok -- Record construction binds even more tightly than application do Ident "T1" <- Lex.lex Punc '{' <- Lex.lex Ident "f1" <- Lex.lex Punc '=' <- Lex.lex x <- ReadP.reset Read.readPrec Punc '}' <- Lex.lex return (T1 { f1 = x })) +++ prec appPrec ( do Ident "T2" <- Lex.lexP x <- ReadP.step Read.readPrec return (T2 x)) ) readListPrec = readListPrecDefault readList = readListDefault \begin{code}
gen_Read_binds :: FixityEnv -> SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds) gen_Read_binds get_fixity loc tycon = (listToBag [read_prec, default_readlist, default_readlistprec], []) where ----------------------------------------------------------------------- default_readlist = mkHsVarBind loc readList_RDR (nlHsVar readListDefault_RDR) default_readlistprec = mkHsVarBind loc readListPrec_RDR (nlHsVar readListPrecDefault_RDR) ----------------------------------------------------------------------- data_cons = tyConDataCons tycon (nullary_cons, non_nullary_cons) = partition isNullarySrcDataCon data_cons read_prec = mkHsVarBind loc readPrec_RDR (nlHsApp (nlHsVar parens_RDR) read_cons) read_cons = foldr1 mk_alt (read_nullary_cons ++ read_non_nullary_cons) read_non_nullary_cons = map read_non_nullary_con non_nullary_cons read_nullary_cons = case nullary_cons of [] -> [] [con] -> [nlHsDo DoExpr (match_con con ++ [noLoc $ mkLastStmt (result_expr con [])])] _ -> [nlHsApp (nlHsVar choose_RDR) (nlList (map mk_pair nullary_cons))] -- NB For operators the parens around (:=:) are matched by the -- enclosing "parens" call, so here we must match the naked -- data_con_str con match_con con | isSym con_str = [symbol_pat con_str] | otherwise = ident_h_pat con_str where con_str = data_con_str con -- For nullary constructors we must match Ident s for normal constrs -- and Symbol s for operators mk_pair con = mkLHsTupleExpr [nlHsLit (mkHsString (data_con_str con)), result_expr con []] read_non_nullary_con data_con | is_infix = mk_parser infix_prec infix_stmts body | is_record = mk_parser record_prec record_stmts body -- Using these two lines instead allows the derived -- read for infix and record bindings to read the prefix form -- | is_infix = mk_alt prefix_parser (mk_parser infix_prec infix_stmts body) -- | is_record = mk_alt prefix_parser (mk_parser record_prec record_stmts body) | otherwise = prefix_parser where body = result_expr data_con as_needed con_str = data_con_str data_con prefix_parser = mk_parser prefix_prec prefix_stmts body read_prefix_con | isSym con_str = [read_punc "(", symbol_pat con_str, read_punc ")"] | otherwise = ident_h_pat con_str read_infix_con | isSym con_str = [symbol_pat con_str] | otherwise = [read_punc "`"] ++ ident_h_pat con_str ++ [read_punc "`"] prefix_stmts -- T a b c = read_prefix_con ++ read_args infix_stmts -- a %% b, or a `T` b = [read_a1] ++ read_infix_con ++ [read_a2] record_stmts -- T { f1 = a, f2 = b } = read_prefix_con ++ [read_punc "{"] ++ concat (intersperse [read_punc ","] field_stmts) ++ [read_punc "}"] field_stmts = zipWithEqual "lbl_stmts" read_field labels as_needed con_arity = dataConSourceArity data_con labels = dataConFieldLabels data_con dc_nm = getName data_con is_infix = dataConIsInfix data_con is_record = length labels > 0 as_needed = take con_arity as_RDRs read_args = zipWithEqual "gen_Read_binds" read_arg as_needed (dataConOrigArgTys data_con) (read_a1:read_a2:_) = read_args prefix_prec = appPrecedence infix_prec = getPrecedence get_fixity dc_nm record_prec = appPrecedence + 1 -- Record construction binds even more tightly -- than application; e.g. T2 T1 {x=2} means T2 (T1 {x=2}) ------------------------------------------------------------------------ -- Helpers ------------------------------------------------------------------------ mk_alt e1 e2 = genOpApp e1 alt_RDR e2 -- e1 +++ e2 mk_parser p ss b = nlHsApps prec_RDR [nlHsIntLit p -- prec p (do { ss ; b }) , nlHsDo DoExpr (ss ++ [noLoc $ mkLastStmt b])] bindLex pat = noLoc (mkBindStmt pat (nlHsVar lexP_RDR)) -- pat <- lexP con_app con as = nlHsVarApps (getRdrName con) as -- con as result_expr con as = nlHsApp (nlHsVar returnM_RDR) (con_app con as) -- return (con as) punc_pat s = nlConPat punc_RDR [nlLitPat (mkHsString s)] -- Punc 'c' -- For constructors and field labels ending in '#', we hackily -- let the lexer generate two tokens, and look for both in sequence -- Thus [Ident "I"; Symbol "#"]. See Trac #5041 ident_h_pat s | Just (ss, '#') <- snocView s = [ ident_pat ss, symbol_pat "#" ] | otherwise = [ ident_pat s ] ident_pat s = bindLex $ nlConPat ident_RDR [nlLitPat (mkHsString s)] -- Ident "foo" <- lexP symbol_pat s = bindLex $ nlConPat symbol_RDR [nlLitPat (mkHsString s)] -- Symbol ">>" <- lexP data_con_str con = occNameString (getOccName con) read_punc c = bindLex (punc_pat c) read_arg a ty = ASSERT( not (isUnLiftedType ty) ) noLoc (mkBindStmt (nlVarPat a) (nlHsVarApps step_RDR [readPrec_RDR])) read_field lbl a = read_lbl lbl ++ [read_punc "=", noLoc (mkBindStmt (nlVarPat a) (nlHsVarApps reset_RDR [readPrec_RDR]))] -- When reading field labels we might encounter -- a = 3 -- _a = 3 -- or (#) = 4 -- Note the parens! read_lbl lbl | isSym lbl_str = [read_punc "(", symbol_pat lbl_str, read_punc ")"] | otherwise = ident_h_pat lbl_str where lbl_str = occNameString (getOccName lbl)\end{code} %************************************************************************ %* * Show instances %* * %************************************************************************ Example infixr 5 :^: data Tree a = Leaf a | Tree a :^: Tree a instance (Show a) => Show (Tree a) where showsPrec d (Leaf m) = showParen (d > app_prec) showStr where showStr = showString "Leaf " . showsPrec (app_prec+1) m showsPrec d (u :^: v) = showParen (d > up_prec) showStr where showStr = showsPrec (up_prec+1) u . showString " :^: " . showsPrec (up_prec+1) v -- Note: right-associativity of :^: ignored up_prec = 5 -- Precedence of :^: app_prec = 10 -- Application has precedence one more than -- the most tightly-binding operator \begin{code}
gen_Show_binds :: FixityEnv -> SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds) gen_Show_binds get_fixity loc tycon = (listToBag [shows_prec, show_list], []) where ----------------------------------------------------------------------- show_list = mkHsVarBind loc showList_RDR (nlHsApp (nlHsVar showList___RDR) (nlHsPar (nlHsApp (nlHsVar showsPrec_RDR) (nlHsIntLit 0)))) ----------------------------------------------------------------------- data_cons = tyConDataCons tycon shows_prec = mk_FunBind loc showsPrec_RDR (map pats_etc data_cons) pats_etc data_con | nullary_con = -- skip the showParen junk... ASSERT(null bs_needed) ([nlWildPat, con_pat], mk_showString_app op_con_str) | otherwise = ([a_Pat, con_pat], showParen_Expr (nlHsPar (genOpApp a_Expr ge_RDR (nlHsLit (HsInt con_prec_plus_one)))) (nlHsPar (nested_compose_Expr show_thingies))) where data_con_RDR = getRdrName data_con con_arity = dataConSourceArity data_con bs_needed = take con_arity bs_RDRs arg_tys = dataConOrigArgTys data_con -- Correspond 1-1 with bs_needed con_pat = nlConVarPat data_con_RDR bs_needed nullary_con = con_arity == 0 labels = dataConFieldLabels data_con lab_fields = length labels record_syntax = lab_fields > 0 dc_nm = getName data_con dc_occ_nm = getOccName data_con con_str = occNameString dc_occ_nm op_con_str = wrapOpParens con_str backquote_str = wrapOpBackquotes con_str show_thingies | is_infix = [show_arg1, mk_showString_app (" " ++ backquote_str ++ " "), show_arg2] | record_syntax = mk_showString_app (op_con_str ++ " {") : show_record_args ++ [mk_showString_app "}"] | otherwise = mk_showString_app (op_con_str ++ " ") : show_prefix_args show_label l = mk_showString_app (nm ++ " = ") -- Note the spaces around the "=" sign. If we don't have them -- then we get Foo { x=-1 } and the "=-" parses as a single -- lexeme. Only the space after the '=' is necessary, but -- it seems tidier to have them both sides. where occ_nm = getOccName l nm = wrapOpParens (occNameString occ_nm) show_args = zipWith show_arg bs_needed arg_tys (show_arg1:show_arg2:_) = show_args show_prefix_args = intersperse (nlHsVar showSpace_RDR) show_args -- Assumption for record syntax: no of fields == no of labelled fields -- (and in same order) show_record_args = concat $ intersperse [mk_showString_app ", "] $ [ [show_label lbl, arg] | (lbl,arg) <- zipEqual "gen_Show_binds" labels show_args ] -- Generates (showsPrec p x) for argument x, but it also boxes -- the argument first if necessary. Note that this prints unboxed -- things without any '#' decorations; could change that if need be show_arg b arg_ty = nlHsApps showsPrec_RDR [nlHsLit (HsInt arg_prec), box_if_necy "Show" tycon (nlHsVar b) arg_ty] -- Fixity stuff is_infix = dataConIsInfix data_con con_prec_plus_one = 1 + getPrec is_infix get_fixity dc_nm arg_prec | record_syntax = 0 -- Record fields don't need parens | otherwise = con_prec_plus_one wrapOpParens :: String -> String wrapOpParens s | isSym s = '(' : s ++ ")" | otherwise = s wrapOpBackquotes :: String -> String wrapOpBackquotes s | isSym s = s | otherwise = '`' : s ++ "`" isSym :: String -> Bool isSym "" = False isSym (c : _) = startsVarSym c || startsConSym c mk_showString_app :: String -> LHsExpr RdrName mk_showString_app str = nlHsApp (nlHsVar showString_RDR) (nlHsLit (mkHsString str))\end{code} \begin{code}
getPrec :: Bool -> FixityEnv -> Name -> Integer getPrec is_infix get_fixity nm | not is_infix = appPrecedence | otherwise = getPrecedence get_fixity nm appPrecedence :: Integer appPrecedence = fromIntegral maxPrecedence + 1 -- One more than the precedence of the most -- tightly-binding operator getPrecedence :: FixityEnv -> Name -> Integer getPrecedence get_fixity nm = case lookupFixity get_fixity nm of Fixity x _assoc -> fromIntegral x -- NB: the Report says that associativity is not taken -- into account for either Read or Show; hence we -- ignore associativity here\end{code} %************************************************************************ %* * \subsection{Typeable} %* * %************************************************************************ From the data type data T a b = .... we generate instance Typeable2 T where typeOf2 _ = mkTyConApp (mkTyCon
gen_Typeable_binds :: SrcSpan -> TyCon -> LHsBinds RdrName gen_Typeable_binds loc tycon = unitBag $ mk_easy_FunBind loc (mk_typeOf_RDR tycon) -- Name of appropriate type0f function [nlWildPat] (nlHsApps mkTyConApp_RDR [tycon_rep, nlList []]) where tycon_name = tyConName tycon modl = nameModule tycon_name pkg = modulePackageId modl modl_fs = moduleNameFS (moduleName modl) pkg_fs = packageIdFS pkg name_fs = occNameFS (nameOccName tycon_name) tycon_rep = nlHsApps mkTyCon_RDR (map nlHsLit [int64 high, int64 low, HsString pkg_fs, HsString modl_fs, HsString name_fs]) hashThis = unwords $ map unpackFS [pkg_fs, modl_fs, name_fs] Fingerprint high low = fingerprintString hashThis int64 | wORD_SIZE == 4 = HsWord64Prim . fromIntegral | otherwise = HsWordPrim . fromIntegral mk_typeOf_RDR :: TyCon -> RdrName -- Use the arity of the TyCon to make the right typeOfn function mk_typeOf_RDR tycon = varQual_RDR tYPEABLE_INTERNAL (mkFastString ("typeOf" ++ suffix)) where arity = tyConArity tycon suffix | arity == 0 = "" | otherwise = show arity\end{code} %************************************************************************ %* * Data instances %* * %************************************************************************ From the data type data T a b = T1 a b | T2 we generate $cT1 = mkDataCon $dT "T1" Prefix $cT2 = mkDataCon $dT "T2" Prefix $dT = mkDataType "Module.T" [] [$con_T1, $con_T2] -- the [] is for field labels. 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 gunfold k z c = case conIndex c of I# 1# -> k (k (z T1)) I# 2# -> z T2 toConstr (T1 _ _) = $cT1 toConstr T2 = $cT2 dataTypeOf _ = $dT dataCast1 = gcast1 -- If T :: * -> * dataCast2 = gcast2 -- if T :: * -> * -> * \begin{code}
gen_Data_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, -- The method bindings DerivAuxBinds) -- Auxiliary bindings gen_Data_binds loc tycon = (listToBag [gfoldl_bind, gunfold_bind, toCon_bind, dataTypeOf_bind] `unionBags` gcast_binds, -- Auxiliary definitions: the data type and constructors MkTyCon tycon : map MkDataCon data_cons) where data_cons = tyConDataCons tycon n_cons = length data_cons one_constr = n_cons == 1 ------------ gfoldl gfoldl_bind = mk_FunBind loc gfoldl_RDR (map gfoldl_eqn data_cons) gfoldl_eqn con = ([nlVarPat k_RDR, nlVarPat z_RDR, nlConVarPat con_name as_needed], foldl mk_k_app (nlHsVar z_RDR `nlHsApp` nlHsVar con_name) as_needed) where con_name :: RdrName con_name = getRdrName con as_needed = take (dataConSourceArity con) as_RDRs mk_k_app e v = nlHsPar (nlHsOpApp e k_RDR (nlHsVar v)) ------------ gunfold gunfold_bind = mk_FunBind loc gunfold_RDR [([k_Pat, z_Pat, if one_constr then nlWildPat else c_Pat], gunfold_rhs)] gunfold_rhs | one_constr = mk_unfold_rhs (head data_cons) -- No need for case | otherwise = nlHsCase (nlHsVar conIndex_RDR `nlHsApp` c_Expr) (map gunfold_alt data_cons) gunfold_alt dc = mkSimpleHsAlt (mk_unfold_pat dc) (mk_unfold_rhs dc) mk_unfold_rhs dc = foldr nlHsApp (nlHsVar z_RDR `nlHsApp` nlHsVar (getRdrName dc)) (replicate (dataConSourceArity dc) (nlHsVar k_RDR)) mk_unfold_pat dc -- Last one is a wild-pat, to avoid -- redundant test, and annoying warning | tag-fIRST_TAG == n_cons-1 = nlWildPat -- Last constructor | otherwise = nlConPat intDataCon_RDR [nlLitPat (HsIntPrim (toInteger tag))] where tag = dataConTag dc ------------ toConstr toCon_bind = mk_FunBind loc toConstr_RDR (map to_con_eqn data_cons) to_con_eqn dc = ([nlWildConPat dc], nlHsVar (mk_constr_name dc)) ------------ dataTypeOf dataTypeOf_bind = mk_easy_FunBind loc dataTypeOf_RDR [nlWildPat] (nlHsVar (mk_data_type_name tycon)) ------------ gcast1/2 tycon_kind = tyConKind tycon gcast_binds | tycon_kind `eqKind` kind1 = mk_gcast dataCast1_RDR gcast1_RDR | tycon_kind `eqKind` kind2 = mk_gcast dataCast2_RDR gcast2_RDR | otherwise = emptyBag mk_gcast dataCast_RDR gcast_RDR = unitBag (mk_easy_FunBind loc dataCast_RDR [nlVarPat f_RDR] (nlHsVar gcast_RDR `nlHsApp` nlHsVar f_RDR)) kind1, kind2 :: Kind kind1 = liftedTypeKind `mkArrowKind` liftedTypeKind kind2 = liftedTypeKind `mkArrowKind` kind1 gfoldl_RDR, gunfold_RDR, toConstr_RDR, dataTypeOf_RDR, mkConstr_RDR, mkDataType_RDR, conIndex_RDR, prefix_RDR, infix_RDR, dataCast1_RDR, dataCast2_RDR, gcast1_RDR, gcast2_RDR, constr_RDR, dataType_RDR :: RdrName gfoldl_RDR = varQual_RDR gENERICS (fsLit "gfoldl") gunfold_RDR = varQual_RDR gENERICS (fsLit "gunfold") toConstr_RDR = varQual_RDR gENERICS (fsLit "toConstr") dataTypeOf_RDR = varQual_RDR gENERICS (fsLit "dataTypeOf") dataCast1_RDR = varQual_RDR gENERICS (fsLit "dataCast1") dataCast2_RDR = varQual_RDR gENERICS (fsLit "dataCast2") gcast1_RDR = varQual_RDR tYPEABLE (fsLit "gcast1") gcast2_RDR = varQual_RDR tYPEABLE (fsLit "gcast2") mkConstr_RDR = varQual_RDR gENERICS (fsLit "mkConstr") constr_RDR = tcQual_RDR gENERICS (fsLit "Constr") mkDataType_RDR = varQual_RDR gENERICS (fsLit "mkDataType") dataType_RDR = tcQual_RDR gENERICS (fsLit "DataType") conIndex_RDR = varQual_RDR gENERICS (fsLit "constrIndex") prefix_RDR = dataQual_RDR gENERICS (fsLit "Prefix") infix_RDR = dataQual_RDR gENERICS (fsLit "Infix")\end{code} %************************************************************************ %* * Functor instances see http://www.mail-archive.com/haskell-prime@haskell.org/msg02116.html %* * %************************************************************************ For the data type: data T a = T1 Int a | T2 (T a) We generate the instance: instance Functor T where fmap f (T1 b1 a) = T1 b1 (f a) fmap f (T2 ta) = T2 (fmap f ta) Notice that we don't simply apply 'fmap' to the constructor arguments. Rather - Do nothing to an argument whose type doesn't mention 'a' - Apply 'f' to an argument of type 'a' - Apply 'fmap f' to other arguments That's why we have to recurse deeply into the constructor argument types, rather than just one level, as we typically do. What about types with more than one type parameter? In general, we only derive Functor for the last position: data S a b = S1 [b] | S2 (a, T a b) instance Functor (S a) where fmap f (S1 bs) = S1 (fmap f bs) fmap f (S2 (p,q)) = S2 (a, fmap f q) However, we have special cases for - tuples - functions More formally, we write the derivation of fmap code over type variable 'a for type 'b as ($fmap 'a 'b). In this general notation the derived instance for T is: instance Functor T where fmap f (T1 x1 x2) = T1 ($(fmap 'a 'b1) x1) ($(fmap 'a 'a) x2) fmap f (T2 x1) = T2 ($(fmap 'a '(T a)) x1) $(fmap 'a 'b) x = x -- when b does not contain a $(fmap 'a 'a) x = f x $(fmap 'a '(b1,b2)) x = case x of (x1,x2) -> ($(fmap 'a 'b1) x1, $(fmap 'a 'b2) x2) $(fmap 'a '(T b1 b2)) x = fmap $(fmap 'a 'b2) x -- when a only occurs in the last parameter, b2 $(fmap 'a '(b -> c)) x = \b -> $(fmap 'a' 'c) (x ($(cofmap 'a 'b) b)) For functions, the type parameter 'a can occur in a contravariant position, which means we need to derive a function like: cofmap :: (a -> b) -> (f b -> f a) This is pretty much the same as $fmap, only without the $(cofmap 'a 'a) case: $(cofmap 'a 'b) x = x -- when b does not contain a $(cofmap 'a 'a) x = error "type variable in contravariant position" $(cofmap 'a '(b1,b2)) x = case x of (x1,x2) -> ($(cofmap 'a 'b1) x1, $(cofmap 'a 'b2) x2) $(cofmap 'a '[b]) x = map $(cofmap 'a 'b) x $(cofmap 'a '(T b1 b2)) x = fmap $(cofmap 'a 'b2) x -- when a only occurs in the last parameter, b2 $(cofmap 'a '(b -> c)) x = \b -> $(cofmap 'a' 'c) (x ($(fmap 'a 'c) b)) \begin{code}
gen_Functor_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds) gen_Functor_binds loc tycon = (unitBag fmap_bind, []) where data_cons = tyConDataCons tycon fmap_bind = L loc $ mkRdrFunBind (L loc fmap_RDR) eqns fmap_eqn con = evalState (match_for_con [f_Pat] con parts) bs_RDRs where parts = foldDataConArgs ft_fmap con eqns | null data_cons = [mkSimpleMatch [nlWildPat, nlWildPat] (error_Expr "Void fmap")] | otherwise = map fmap_eqn data_cons 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 return (nlHsApps con_name xs) -- Con (g1 v1) (g2 v2) ..\end{code} Utility functions related to Functor deriving. Since several things use the same pattern of traversal, this is abstracted into functorLikeTraverse. This function works like a fold: it makes a value of type 'a' in a bottom up way. \begin{code}
-- Generic traversal for Functor deriving 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) go co (FunTy (PredTy _) b) = go co b go co (FunTy x y) | xc || yc = (caseFun xr yr,True) where (xr,xc) = go (not co) x (yr,yc) = go co y go co (AppTy x y) | xc = (caseWrongArg, True) | yc = (caseTyApp x yr, True) where (_, xc) = go co x (yr,yc) = go co y go co ty@(TyConApp con args) | not (or xcs) = (caseTrivial, False) -- Variable does not occur -- At this point we know that xrs, xcs is not empty, -- and at least one xr is True | isTupleTyCon con = (caseTuple (tupleTyConBoxity con) xrs, True) | or (init xcs) = (caseWrongArg, True) -- T (..var..) ty | otherwise = -- T (..no var..) ty (caseTyApp (fst (splitAppTy ty)) (last xrs), True) where (xrs,xcs) = unzip (map (go co) args) go co (ForAllTy v x) | v /= var && xc = (caseForAll v xr,True) where (xr,xc) = go co x go _ _ = (caseTrivial,False) -- Return all syntactic subterms of ty that contain var somewhere -- These are the things that should appear in instance constraints 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 body <- lam (nlHsVar n) return (mkHsLam [nlVarPat n] body) mkSimpleLam2 :: (LHsExpr id -> LHsExpr id -> State [id] (LHsExpr id)) -> State [id] (LHsExpr id) mkSimpleLam2 lam = do (n1:n2:names) <- get put names body <- lam (nlHsVar n1) (nlHsVar n2) return (mkHsLam [nlVarPat n1,nlVarPat n2] body) -- "Con a1 a2 a3 -> fold [x1 a1, x2 a2, x3 a3]" mkSimpleConMatch :: Monad m => (RdrName -> [a] -> m (LHsExpr RdrName)) -> [LPat RdrName] -> DataCon -> [LHsExpr RdrName -> a] -> m (LMatch RdrName) mkSimpleConMatch fold extra_pats con insides = do let con_name = getRdrName con let vars_needed = takeList insides as_RDRs let pat = nlConVarPat con_name vars_needed rhs <- fold con_name (zipWith ($) insides (map nlHsVar vars_needed)) return $ mkMatch (extra_pats ++ [pat]) rhs emptyLocalBinds -- "case x of (a1,a2,a3) -> fold [x1 a1, x2 a2, x3 a3]" mkSimpleTupleCase :: Monad m => ([LPat RdrName] -> DataCon -> [LHsExpr RdrName -> a] -> m (LMatch RdrName)) -> Boxity -> [LHsExpr RdrName -> a] -> LHsExpr RdrName -> m (LHsExpr RdrName) mkSimpleTupleCase match_for_con boxity insides x = do let con = tupleCon boxity (length insides) match <- match_for_con [] con insides return $ nlHsCase x [match]\end{code} %************************************************************************ %* * Foldable instances see http://www.mail-archive.com/haskell-prime@haskell.org/msg02116.html %* * %************************************************************************ Deriving Foldable instances works the same way as Functor instances, only Foldable instances are not possible for function types at all. Here the derived instance for the type T above is: instance Foldable T where foldr f z (T1 x1 x2 x3) = $(foldr 'a 'b1) x1 ( $(foldr 'a 'a) x2 ( $(foldr 'a 'b2) x3 z ) ) The cases are: $(foldr 'a 'b) x z = z -- when b does not contain a $(foldr 'a 'a) x z = f x z $(foldr 'a '(b1,b2)) x z = case x of (x1,x2) -> $(foldr 'a 'b1) x1 ( $(foldr 'a 'b2) x2 z ) $(foldr 'a '(T b1 b2)) x z = foldr $(foldr 'a 'b2) x z -- when a only occurs in the last parameter, b2 Note that the arguments to the real foldr function are the wrong way around, since (f :: a -> b -> b), while (foldr f :: b -> t a -> b). \begin{code}
gen_Foldable_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds) gen_Foldable_binds loc tycon = (unitBag foldr_bind, []) where data_cons = tyConDataCons tycon foldr_bind = L loc $ mkRdrFunBind (L loc foldable_foldr_RDR) eqns eqns = map foldr_eqn data_cons foldr_eqn con = evalState (match_for_con z_Expr [f_Pat,z_Pat] con parts) bs_RDRs 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} %************************************************************************ %* * Traversable instances see http://www.mail-archive.com/haskell-prime@haskell.org/msg02116.html %* * %************************************************************************ Again, Traversable is much like Functor and Foldable. The cases are: $(traverse 'a 'b) x = pure x -- when b does not contain a $(traverse 'a 'a) x = f x $(traverse 'a '(b1,b2)) x = case x of (x1,x2) -> (,) <$> $(traverse 'a 'b1) x1 <*> $(traverse 'a 'b2) x2 $(traverse 'a '(T b1 b2)) x = traverse $(traverse 'a 'b2) x -- when a only occurs in the last parameter, b2 Note that the generated code is not as efficient as it could be. For instance: data T a = T Int a deriving Traversable gives the function: traverse f (T x y) = T <$> pure x <*> f y instead of: traverse f (T x y) = T x <$> f y \begin{code}
gen_Traversable_binds :: SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds) gen_Traversable_binds loc tycon = (unitBag traverse_bind, []) where data_cons = tyConDataCons tycon traverse_bind = L loc $ mkRdrFunBind (L loc traverse_RDR) eqns eqns = map traverse_eqn data_cons traverse_eqn con = evalState (match_for_con [f_Pat] con parts) bs_RDRs 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 return (mkApCon (nlHsVar con_name) xs) -- ((Con <$> x1) <*> x2) <*> .. mkApCon con [] = nlHsApps pure_RDR [con] mkApCon con (x:xs) = foldl appAp (nlHsApps fmap_RDR [con,x]) xs where appAp x y = nlHsApps ap_RDR [x,y]\end{code} %************************************************************************ %* * \subsection{Generating extra binds (@con2tag@ and @tag2con@)} %* * %************************************************************************ \begin{verbatim} data Foo ... = ... con2tag_Foo :: Foo ... -> Int# tag2con_Foo :: Int -> Foo ... -- easier if Int, not Int# maxtag_Foo :: Int -- ditto (NB: not unlifted) \end{verbatim} The `tags' here start at zero, hence the @fIRST_TAG@ (currently one) fiddling around. \begin{code}
genAuxBind :: SrcSpan -> DerivAuxBind -> (LHsBind RdrName, LSig RdrName) genAuxBind loc (GenCon2Tag tycon) = (mk_FunBind loc rdr_name eqns, L loc (TypeSig [L loc rdr_name] (L loc sig_ty))) where rdr_name = con2tag_RDR tycon sig_ty = HsCoreTy $ mkSigmaTy (tyConTyVars tycon) (tyConStupidTheta tycon) $ mkParentType tycon `mkFunTy` intPrimTy lots_of_constructors = tyConFamilySize tycon > 8 -- was: mAX_FAMILY_SIZE_FOR_VEC_RETURNS -- but we don't do vectored returns any more. eqns | lots_of_constructors = [get_tag_eqn] | otherwise = map mk_eqn (tyConDataCons tycon) get_tag_eqn = ([nlVarPat a_RDR], nlHsApp (nlHsVar getTag_RDR) a_Expr) mk_eqn :: DataCon -> ([LPat RdrName], LHsExpr RdrName) mk_eqn con = ([nlWildConPat con], nlHsLit (HsIntPrim (toInteger ((dataConTag con) - fIRST_TAG)))) genAuxBind loc (GenTag2Con tycon) = (mk_FunBind loc rdr_name [([nlConVarPat intDataCon_RDR [a_RDR]], nlHsApp (nlHsVar tagToEnum_RDR) a_Expr)], L loc (TypeSig [L loc rdr_name] (L loc sig_ty))) where sig_ty = HsCoreTy $ mkForAllTys (tyConTyVars tycon) $ intTy `mkFunTy` mkParentType tycon rdr_name = tag2con_RDR tycon genAuxBind loc (GenMaxTag tycon) = (mkHsVarBind loc rdr_name rhs, L loc (TypeSig [L loc rdr_name] (L loc sig_ty))) where rdr_name = maxtag_RDR tycon sig_ty = HsCoreTy intTy rhs = nlHsApp (nlHsVar intDataCon_RDR) (nlHsLit (HsIntPrim max_tag)) max_tag = case (tyConDataCons tycon) of data_cons -> toInteger ((length data_cons) - fIRST_TAG) genAuxBind loc (MkTyCon tycon) -- $dT = (mkHsVarBind loc rdr_name rhs, L loc (TypeSig [L loc rdr_name] sig_ty)) where rdr_name = mk_data_type_name tycon sig_ty = nlHsTyVar dataType_RDR constrs = [nlHsVar (mk_constr_name con) | con <- tyConDataCons tycon] rhs = nlHsVar mkDataType_RDR `nlHsApp` nlHsLit (mkHsString (showSDocOneLine (ppr tycon))) `nlHsApp` nlList constrs genAuxBind loc (MkDataCon dc) -- $cT1 etc = (mkHsVarBind loc rdr_name rhs, L loc (TypeSig [L loc rdr_name] sig_ty)) where rdr_name = mk_constr_name dc sig_ty = nlHsTyVar constr_RDR rhs = nlHsApps mkConstr_RDR constr_args constr_args = [ -- nlHsIntLit (toInteger (dataConTag dc)), -- Tag nlHsVar (mk_data_type_name (dataConTyCon dc)), -- DataType nlHsLit (mkHsString (occNameString dc_occ)), -- String name nlList labels, -- Field labels nlHsVar fixity] -- Fixity labels = map (nlHsLit . mkHsString . getOccString) (dataConFieldLabels dc) dc_occ = getOccName dc is_infix = isDataSymOcc dc_occ fixity | is_infix = infix_RDR | otherwise = prefix_RDR mk_data_type_name :: TyCon -> RdrName -- "$tT" mk_data_type_name tycon = mkAuxBinderName (tyConName tycon) mkDataTOcc mk_constr_name :: DataCon -> RdrName -- "$cC" mk_constr_name con = mkAuxBinderName (dataConName con) mkDataCOcc mkParentType :: TyCon -> Type -- Turn the representation tycon of a family into -- a use of its family constructor mkParentType tc = case tyConFamInst_maybe tc of Nothing -> mkTyConApp tc (mkTyVarTys (tyConTyVars tc)) Just (fam_tc,tys) -> mkTyConApp fam_tc tys\end{code} %************************************************************************ %* * \subsection{Utility bits for generating bindings} %* * %************************************************************************ \begin{code}
mk_FunBind :: SrcSpan -> RdrName -> [([LPat RdrName], LHsExpr RdrName)] -> LHsBind RdrName mk_FunBind loc fun pats_and_exprs = L loc $ mkRdrFunBind (L loc fun) matches where matches = [mkMatch p e emptyLocalBinds | (p,e) <-pats_and_exprs] mkRdrFunBind :: Located RdrName -> [LMatch RdrName] -> HsBind RdrName mkRdrFunBind fun@(L _ fun_rdr) matches | null matches = mkFunBind fun [mkMatch [] (error_Expr str) emptyLocalBinds] -- Catch-all eqn looks like -- fmap = error "Void fmap" -- It's needed if there no data cons at all, -- which can happen with -XEmptyDataDecls -- See Trac #4302 | otherwise = mkFunBind fun matches where str = "Void " ++ occNameString (rdrNameOcc fun_rdr)\end{code} \begin{code}
box_if_necy :: String -- The class involved -> TyCon -- The tycon involved -> LHsExpr RdrName -- The argument -> Type -- The argument type -> LHsExpr RdrName -- Boxed version of the arg box_if_necy cls_str tycon arg arg_ty | isUnLiftedType arg_ty = nlHsApp (nlHsVar box_con) arg | otherwise = arg where box_con = assoc_ty_id cls_str tycon box_con_tbl arg_ty --------------------- primOrdOps :: String -- The class involved -> TyCon -- The tycon involved -> Type -- The type -> (PrimOp, PrimOp, PrimOp, PrimOp, PrimOp) -- (lt,le,eq,ge,gt) primOrdOps str tycon ty = assoc_ty_id str tycon ord_op_tbl ty ord_op_tbl :: [(Type, (PrimOp, PrimOp, PrimOp, PrimOp, PrimOp))] ord_op_tbl = [(charPrimTy, (CharLtOp, CharLeOp, CharEqOp, CharGeOp, CharGtOp)) ,(intPrimTy, (IntLtOp, IntLeOp, IntEqOp, IntGeOp, IntGtOp)) ,(wordPrimTy, (WordLtOp, WordLeOp, WordEqOp, WordGeOp, WordGtOp)) ,(addrPrimTy, (AddrLtOp, AddrLeOp, AddrEqOp, AddrGeOp, AddrGtOp)) ,(floatPrimTy, (FloatLtOp, FloatLeOp, FloatEqOp, FloatGeOp, FloatGtOp)) ,(doublePrimTy, (DoubleLtOp, DoubleLeOp, DoubleEqOp, DoubleGeOp, DoubleGtOp)) ] box_con_tbl :: [(Type, RdrName)] box_con_tbl = [(charPrimTy, getRdrName charDataCon) ,(intPrimTy, getRdrName intDataCon) ,(wordPrimTy, wordDataCon_RDR) ,(floatPrimTy, getRdrName floatDataCon) ,(doublePrimTy, getRdrName doubleDataCon) ] assoc_ty_id :: String -- The class involved -> TyCon -- The tycon involved -> [(Type,a)] -- The table -> Type -- The type -> a -- The result of the lookup assoc_ty_id cls_str _ tbl ty | null res = pprPanic "Error in deriving:" (text "Can't derive" <+> text cls_str <+> text "for primitive type" <+> ppr ty) | otherwise = head res where res = [id | (ty',id) <- tbl, ty `eqType` ty'] ----------------------------------------------------------------------- and_Expr :: LHsExpr RdrName -> LHsExpr RdrName -> LHsExpr RdrName and_Expr a b = genOpApp a and_RDR b ----------------------------------------------------------------------- eq_Expr :: TyCon -> Type -> LHsExpr RdrName -> LHsExpr RdrName -> LHsExpr RdrName eq_Expr tycon ty a b = genOpApp a eq_op b where eq_op | not (isUnLiftedType ty) = eq_RDR | otherwise = primOpRdrName prim_eq (_, _, prim_eq, _, _) = primOrdOps "Eq" tycon ty\end{code} \begin{code}
untag_Expr :: TyCon -> [( RdrName, RdrName)] -> LHsExpr RdrName -> LHsExpr RdrName untag_Expr _ [] expr = expr untag_Expr tycon ((untag_this, put_tag_here) : more) expr = nlHsCase (nlHsPar (nlHsVarApps (con2tag_RDR tycon) [untag_this])) {-of-} [mkSimpleHsAlt (nlVarPat put_tag_here) (untag_Expr tycon more expr)] enum_from_to_Expr :: LHsExpr RdrName -> LHsExpr RdrName -> LHsExpr RdrName enum_from_then_to_Expr :: LHsExpr RdrName -> LHsExpr RdrName -> LHsExpr RdrName -> LHsExpr RdrName enum_from_to_Expr f t2 = nlHsApp (nlHsApp (nlHsVar enumFromTo_RDR) f) t2 enum_from_then_to_Expr f t t2 = nlHsApp (nlHsApp (nlHsApp (nlHsVar enumFromThenTo_RDR) f) t) t2 showParen_Expr :: LHsExpr RdrName -> LHsExpr RdrName -> LHsExpr RdrName showParen_Expr e1 e2 = nlHsApp (nlHsApp (nlHsVar showParen_RDR) e1) e2 nested_compose_Expr :: [LHsExpr RdrName] -> LHsExpr RdrName nested_compose_Expr [] = panic "nested_compose_expr" -- Arg is always non-empty nested_compose_Expr [e] = parenify e nested_compose_Expr (e:es) = nlHsApp (nlHsApp (nlHsVar compose_RDR) (parenify e)) (nested_compose_Expr es) -- impossible_Expr is used in case RHSs that should never happen. -- We generate these to keep the desugarer from complaining that they *might* happen! error_Expr :: String -> LHsExpr RdrName error_Expr string = nlHsApp (nlHsVar error_RDR) (nlHsLit (mkHsString string)) -- illegal_Expr is used when signalling error conditions in the RHS of a derived -- method. It is currently only used by Enum.{succ,pred} illegal_Expr :: String -> String -> String -> LHsExpr RdrName illegal_Expr meth tp msg = nlHsApp (nlHsVar error_RDR) (nlHsLit (mkHsString (meth ++ '{':tp ++ "}: " ++ msg))) -- illegal_toEnum_tag is an extended version of illegal_Expr, which also allows you -- to include the value of a_RDR in the error string. illegal_toEnum_tag :: String -> RdrName -> LHsExpr RdrName illegal_toEnum_tag tp maxtag = nlHsApp (nlHsVar error_RDR) (nlHsApp (nlHsApp (nlHsVar append_RDR) (nlHsLit (mkHsString ("toEnum{" ++ tp ++ "}: tag (")))) (nlHsApp (nlHsApp (nlHsApp (nlHsVar showsPrec_RDR) (nlHsIntLit 0)) (nlHsVar a_RDR)) (nlHsApp (nlHsApp (nlHsVar append_RDR) (nlHsLit (mkHsString ") is outside of enumeration's range (0,"))) (nlHsApp (nlHsApp (nlHsApp (nlHsVar showsPrec_RDR) (nlHsIntLit 0)) (nlHsVar maxtag)) (nlHsLit (mkHsString ")")))))) parenify :: LHsExpr RdrName -> LHsExpr RdrName parenify e@(L _ (HsVar _)) = e parenify e = mkHsPar e -- genOpApp wraps brackets round the operator application, so that the -- renamer won't subsequently try to re-associate it. genOpApp :: LHsExpr RdrName -> RdrName -> LHsExpr RdrName -> LHsExpr RdrName genOpApp e1 op e2 = nlHsPar (nlHsOpApp e1 op e2)\end{code} \begin{code}
a_RDR, b_RDR, c_RDR, d_RDR, f_RDR, k_RDR, z_RDR, ah_RDR, bh_RDR, ch_RDR, dh_RDR :: RdrName a_RDR = mkVarUnqual (fsLit "a") b_RDR = mkVarUnqual (fsLit "b") c_RDR = mkVarUnqual (fsLit "c") d_RDR = mkVarUnqual (fsLit "d") f_RDR = mkVarUnqual (fsLit "f") k_RDR = mkVarUnqual (fsLit "k") z_RDR = mkVarUnqual (fsLit "z") ah_RDR = mkVarUnqual (fsLit "a#") bh_RDR = mkVarUnqual (fsLit "b#") ch_RDR = mkVarUnqual (fsLit "c#") dh_RDR = mkVarUnqual (fsLit "d#") as_RDRs, bs_RDRs, cs_RDRs :: [RdrName] as_RDRs = [ mkVarUnqual (mkFastString ("a"++show i)) | i <- [(1::Int) .. ] ] bs_RDRs = [ mkVarUnqual (mkFastString ("b"++show i)) | i <- [(1::Int) .. ] ] cs_RDRs = [ mkVarUnqual (mkFastString ("c"++show i)) | i <- [(1::Int) .. ] ] a_Expr, c_Expr, f_Expr, z_Expr, ltTag_Expr, eqTag_Expr, gtTag_Expr, false_Expr, true_Expr :: LHsExpr RdrName a_Expr = nlHsVar a_RDR -- b_Expr = nlHsVar b_RDR c_Expr = nlHsVar c_RDR f_Expr = nlHsVar f_RDR z_Expr = nlHsVar z_RDR ltTag_Expr = nlHsVar ltTag_RDR eqTag_Expr = nlHsVar eqTag_RDR gtTag_Expr = nlHsVar gtTag_RDR false_Expr = nlHsVar false_RDR true_Expr = nlHsVar true_RDR a_Pat, b_Pat, c_Pat, d_Pat, f_Pat, k_Pat, z_Pat :: LPat RdrName a_Pat = nlVarPat a_RDR b_Pat = nlVarPat b_RDR c_Pat = nlVarPat c_RDR d_Pat = nlVarPat d_RDR f_Pat = nlVarPat f_RDR k_Pat = nlVarPat k_RDR z_Pat = nlVarPat z_RDR con2tag_RDR, tag2con_RDR, maxtag_RDR :: TyCon -> RdrName -- Generates Orig s RdrName, for the binding positions con2tag_RDR tycon = mk_tc_deriv_name tycon mkCon2TagOcc tag2con_RDR tycon = mk_tc_deriv_name tycon mkTag2ConOcc maxtag_RDR tycon = mk_tc_deriv_name tycon mkMaxTagOcc mk_tc_deriv_name :: TyCon -> (OccName -> OccName) -> RdrName mk_tc_deriv_name tycon occ_fun = mkAuxBinderName (tyConName tycon) occ_fun mkAuxBinderName :: Name -> (OccName -> OccName) -> RdrName mkAuxBinderName parent occ_fun = mkRdrUnqual (occ_fun (nameOccName parent)) -- Was: mkDerivedRdrName name occ_fun, which made an original name -- But: (a) that does not work well for standalone-deriving -- (b) an unqualified name is just fine, provided it can't clash with user code\end{code} s RdrName for PrimOps. Can't be done in PrelNames, because PrimOp imports PrelNames, so PrelNames can't import PrimOp. \begin{code}
primOpRdrName :: PrimOp -> RdrName primOpRdrName op = getRdrName (primOpId op) minusInt_RDR, eqInt_RDR, ltInt_RDR, geInt_RDR, gtInt_RDR, leInt_RDR, tagToEnum_RDR :: RdrName minusInt_RDR = primOpRdrName IntSubOp eqInt_RDR = primOpRdrName IntEqOp ltInt_RDR = primOpRdrName IntLtOp geInt_RDR = primOpRdrName IntGeOp gtInt_RDR = primOpRdrName IntGtOp leInt_RDR = primOpRdrName IntLeOp tagToEnum_RDR = primOpRdrName TagToEnumOp error_RDR :: RdrName error_RDR = getRdrName eRROR_ID\end{code}