1 -----------------------------------------------------------------------------
4 -- Copyright : (c) The University of Glasgow, CWI 2001--2004
5 -- License : BSD-style (see the file libraries/base/LICENSE)
7 -- Maintainer : libraries@haskell.org
8 -- Stability : experimental
9 -- Portability : non-portable (local universal quantification)
11 -- \"Scrap your boilerplate\" --- Generic programming in Haskell.
12 -- See <http://www.cs.vu.nl/boilerplate/>. This module provides
13 -- the 'Data' class with its primitives for generic programming, along
14 -- with instances for many datatypes. It corresponds to a merge between
15 -- the previous "Data.Generics.Basics" and almost all of
16 -- "Data.Generics.Instances". The instances that are not present
17 -- in this module were moved to the @Data.Generics.Instances@ module
18 -- in the @syb@ package.
20 -- For more information, please visit the new
21 -- SYB wiki: <http://www.cs.uu.nl/wiki/bin/view/GenericProgramming/SYB>.
24 -----------------------------------------------------------------------------
28 -- * Module Data.Typeable re-exported for convenience
31 -- * The Data class for processing constructor applications
33 gfoldl, -- :: ... -> a -> c a
34 gunfold, -- :: ... -> Constr -> c a
35 toConstr, -- :: a -> Constr
36 dataTypeOf, -- :: a -> DataType
37 dataCast1, -- mediate types and unary type constructors
38 dataCast2, -- mediate types and binary type constructors
39 -- Generic maps defined in terms of gfoldl
50 -- * Datatype representations
51 DataType, -- abstract, instance of: Show
53 mkDataType, -- :: String -> [Constr] -> DataType
54 mkIntType, -- :: String -> DataType
55 mkFloatType, -- :: String -> DataType
56 mkStringType, -- :: String -> DataType
57 mkCharType, -- :: String -> DataType
58 mkNoRepType, -- :: String -> DataType
59 mkNorepType, -- :: String -> DataType
61 dataTypeName, -- :: DataType -> String
62 DataRep(..), -- instance of: Eq, Show
63 dataTypeRep, -- :: DataType -> DataRep
64 -- ** Convenience functions
65 repConstr, -- :: DataType -> ConstrRep -> Constr
66 isAlgType, -- :: DataType -> Bool
67 dataTypeConstrs,-- :: DataType -> [Constr]
68 indexConstr, -- :: DataType -> ConIndex -> Constr
69 maxConstrIndex, -- :: DataType -> ConIndex
70 isNorepType, -- :: DataType -> Bool
72 -- * Data constructor representations
73 Constr, -- abstract, instance of: Eq, Show
74 ConIndex, -- alias for Int, start at 1
75 Fixity(..), -- instance of: Eq, Show
77 mkConstr, -- :: DataType -> String -> Fixity -> Constr
78 mkIntConstr, -- :: DataType -> Integer -> Constr
79 mkFloatConstr, -- :: DataType -> Double -> Constr
80 mkIntegralConstr,-- :: (Integral a) => DataType -> a -> Constr
81 mkRealConstr, -- :: (Real a) => DataType -> a -> Constr
82 mkStringConstr, -- :: DataType -> String -> Constr
83 mkCharConstr, -- :: DataType -> Char -> Constr
85 constrType, -- :: Constr -> DataType
86 ConstrRep(..), -- instance of: Eq, Show
87 constrRep, -- :: Constr -> ConstrRep
88 constrFields, -- :: Constr -> [String]
89 constrFixity, -- :: Constr -> Fixity
90 -- ** Convenience function: algebraic data types
91 constrIndex, -- :: Constr -> ConIndex
92 -- ** From strings to constructors and vice versa: all data types
93 showConstr, -- :: Constr -> String
94 readConstr, -- :: DataType -> String -> Maybe Constr
96 -- * Convenience functions: take type constructors apart
97 tyconUQname, -- :: String -> String
98 tyconModule, -- :: String -> String
100 -- * Generic operations defined in terms of 'gunfold'
101 fromConstr, -- :: Constr -> a
102 fromConstrB, -- :: ... -> Constr -> a
103 fromConstrM -- :: Monad m => ... -> Constr -> m a
108 ------------------------------------------------------------------------------
110 import Prelude -- necessary to get dependencies right
116 -- Imports for the instances
118 import Data.Int -- So we can give Data instance for Int8, ...
119 import Data.Word -- So we can give Data instance for Word8, ...
120 #ifdef __GLASGOW_HASKELL__
121 import GHC.Real( Ratio(..) ) -- So we can give Data instance for Ratio
122 --import GHC.IOBase -- So we can give Data instance for IO, Handle
123 import GHC.Ptr -- So we can give Data instance for Ptr
124 import GHC.ForeignPtr -- So we can give Data instance for ForeignPtr
125 --import GHC.Stable -- So we can give Data instance for StablePtr
126 --import GHC.ST -- So we can give Data instance for ST
127 --import GHC.Conc -- So we can give Data instance for MVar & Co.
128 import GHC.Arr -- So we can give Data instance for Array
131 import Hugs.Prelude( Ratio(..) )
134 import Foreign.ForeignPtr
138 #include "Typeable.h"
142 ------------------------------------------------------------------------------
146 ------------------------------------------------------------------------------
149 The 'Data' class comprehends a fundamental primitive 'gfoldl' for
150 folding over constructor applications, say terms. This primitive can
151 be instantiated in several ways to map over the immediate subterms
152 of a term; see the @gmap@ combinators later in this class. Indeed, a
153 generic programmer does not necessarily need to use the ingenious gfoldl
154 primitive but rather the intuitive @gmap@ combinators. The 'gfoldl'
155 primitive is completed by means to query top-level constructors, to
156 turn constructor representations into proper terms, and to list all
157 possible datatype constructors. This completion allows us to serve
158 generic programming scenarios like read, show, equality, term generation.
160 The combinators 'gmapT', 'gmapQ', 'gmapM', etc are all provided with
161 default definitions in terms of 'gfoldl', leaving open the opportunity
162 to provide datatype-specific definitions.
163 (The inclusion of the @gmap@ combinators as members of class 'Data'
164 allows the programmer or the compiler to derive specialised, and maybe
165 more efficient code per datatype. /Note/: 'gfoldl' is more higher-order
166 than the @gmap@ combinators. This is subject to ongoing benchmarking
167 experiments. It might turn out that the @gmap@ combinators will be
168 moved out of the class 'Data'.)
170 Conceptually, the definition of the @gmap@ combinators in terms of the
171 primitive 'gfoldl' requires the identification of the 'gfoldl' function
172 arguments. Technically, we also need to identify the type constructor
173 @c@ for the construction of the result type from the folded term type.
175 In the definition of @gmapQ@/x/ combinators, we use phantom type
176 constructors for the @c@ in the type of 'gfoldl' because the result type
177 of a query does not involve the (polymorphic) type of the term argument.
178 In the definition of 'gmapQl' we simply use the plain constant type
179 constructor because 'gfoldl' is left-associative anyway and so it is
180 readily suited to fold a left-associative binary operation over the
181 immediate subterms. In the definition of gmapQr, extra effort is
182 needed. We use a higher-order accumulation trick to mediate between
183 left-associative constructor application vs. right-associative binary
184 operation (e.g., @(:)@). When the query is meant to compute a value
185 of type @r@, then the result type withing generic folding is @r -> r@.
186 So the result of folding is a function to which we finally pass the
189 With the @-XDeriveDataTypeable@ option, GHC can generate instances of the
190 'Data' class automatically. For example, given the declaration
192 > data T a b = C1 a b | C2 deriving (Typeable, Data)
194 GHC will generate an instance that is equivalent to
196 > instance (Data a, Data b) => Data (T a b) where
197 > gfoldl k z (C1 a b) = z C1 `k` a `k` b
198 > gfoldl k z C2 = z C2
200 > gunfold k z c = case constrIndex c of
204 > toConstr (C1 _ _) = con_C1
205 > toConstr C2 = con_C2
207 > dataTypeOf _ = ty_T
209 > con_C1 = mkConstr ty_T "C1" [] Prefix
210 > con_C2 = mkConstr ty_T "C2" [] Prefix
211 > ty_T = mkDataType "Module.T" [con_C1, con_C2]
213 This is suitable for datatypes that are exported transparently.
217 class Typeable a => Data a where
219 -- | Left-associative fold operation for constructor applications.
221 -- The type of 'gfoldl' is a headache, but operationally it is a simple
222 -- generalisation of a list fold.
224 -- The default definition for 'gfoldl' is @'const' 'id'@, which is
225 -- suitable for abstract datatypes with no substructures.
226 gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b)
227 -- ^ defines how nonempty constructor applications are
228 -- folded. It takes the folded tail of the constructor
229 -- application and its head, i.e., an immediate subterm,
230 -- and combines them in some way.
231 -> (forall g. g -> c g)
232 -- ^ defines how the empty constructor application is
233 -- folded, like the neutral \/ start element for list
236 -- ^ structure to be folded.
238 -- ^ result, with a type defined in terms of @a@, but
239 -- variability is achieved by means of type constructor
240 -- @c@ for the construction of the actual result type.
242 -- See the 'Data' instances in this file for an illustration of 'gfoldl'.
246 -- | Unfolding constructor applications
247 gunfold :: (forall b r. Data b => c (b -> r) -> c r)
248 -> (forall r. r -> c r)
252 -- | Obtaining the constructor from a given datum.
253 -- For proper terms, this is meant to be the top-level constructor.
254 -- Primitive datatypes are here viewed as potentially infinite sets of
255 -- values (i.e., constructors).
256 toConstr :: a -> Constr
259 -- | The outer type constructor of the type
260 dataTypeOf :: a -> DataType
264 ------------------------------------------------------------------------------
266 -- Mediate types and type constructors
268 ------------------------------------------------------------------------------
270 -- | Mediate types and unary type constructors.
271 -- In 'Data' instances of the form @T a@, 'dataCast1' should be defined
274 -- The default definition is @'const' 'Nothing'@, which is appropriate
275 -- for non-unary type constructors.
276 dataCast1 :: Typeable1 t
277 => (forall d. Data d => c (t d))
279 dataCast1 _ = Nothing
281 -- | Mediate types and binary type constructors.
282 -- In 'Data' instances of the form @T a b@, 'dataCast2' should be
283 -- defined as 'gcast2'.
285 -- The default definition is @'const' 'Nothing'@, which is appropriate
286 -- for non-binary type constructors.
287 dataCast2 :: Typeable2 t
288 => (forall d e. (Data d, Data e) => c (t d e))
290 dataCast2 _ = Nothing
294 ------------------------------------------------------------------------------
296 -- Typical generic maps defined in terms of gfoldl
298 ------------------------------------------------------------------------------
301 -- | A generic transformation that maps over the immediate subterms
303 -- The default definition instantiates the type constructor @c@ in the
304 -- type of 'gfoldl' to an identity datatype constructor, using the
305 -- isomorphism pair as injection and projection.
306 gmapT :: (forall b. Data b => b -> b) -> a -> a
308 -- Use an identity datatype constructor ID (see below)
309 -- to instantiate the type constructor c in the type of gfoldl,
310 -- and perform injections ID and projections unID accordingly.
312 gmapT f x0 = unID (gfoldl k ID x0)
314 k (ID c) x = ID (c (f x))
317 -- | A generic query with a left-associative binary operator
318 gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> a -> r
319 gmapQl o r f = unCONST . gfoldl k z
321 k c x = CONST $ (unCONST c) `o` f x
324 -- | A generic query with a right-associative binary operator
325 gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> a -> r
326 gmapQr o r0 f x0 = unQr (gfoldl k (const (Qr id)) x0) r0
328 k (Qr c) x = Qr (\r -> c (f x `o` r))
331 -- | A generic query that processes the immediate subterms and returns a list
332 -- of results. The list is given in the same order as originally specified
333 -- in the declaratoin of the data constructors.
334 gmapQ :: (forall d. Data d => d -> u) -> a -> [u]
335 gmapQ f = gmapQr (:) [] f
338 -- | A generic query that processes one child by index (zero-based)
339 gmapQi :: Int -> (forall d. Data d => d -> u) -> a -> u
340 gmapQi i f x = case gfoldl k z x of { Qi _ q -> fromJust q }
342 k (Qi i' q) a = Qi (i'+1) (if i==i' then Just (f a) else q)
346 -- | A generic monadic transformation that maps over the immediate subterms
348 -- The default definition instantiates the type constructor @c@ in
349 -- the type of 'gfoldl' to the monad datatype constructor, defining
350 -- injection and projection using 'return' and '>>='.
351 gmapM :: Monad m => (forall d. Data d => d -> m d) -> a -> m a
353 -- Use immediately the monad datatype constructor
354 -- to instantiate the type constructor c in the type of gfoldl,
355 -- so injection and projection is done by return and >>=.
357 gmapM f = gfoldl k return
364 -- | Transformation of at least one immediate subterm does not fail
365 gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> a -> m a
369 The type constructor that we use here simply keeps track of the fact
370 if we already succeeded for an immediate subterm; see Mp below. To
371 this end, we couple the monadic computation with a Boolean.
375 gmapMp f x = unMp (gfoldl k z x) >>= \(x',b) ->
376 if b then return x' else mzero
378 z g = Mp (return (g,False))
380 = Mp ( c >>= \(h, b) ->
381 (f y >>= \y' -> return (h y', True))
382 `mplus` return (h y, b)
385 -- | Transformation of one immediate subterm with success
386 gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> a -> m a
390 We use the same pairing trick as for gmapMp,
391 i.e., we use an extra Bool component to keep track of the
392 fact whether an immediate subterm was processed successfully.
393 However, we cut of mapping over subterms once a first subterm
394 was transformed successfully.
398 gmapMo f x = unMp (gfoldl k z x) >>= \(x',b) ->
399 if b then return x' else mzero
401 z g = Mp (return (g,False))
403 = Mp ( c >>= \(h,b) -> if b
405 else (f y >>= \y' -> return (h y',True))
406 `mplus` return (h y, b)
410 -- | The identity type constructor needed for the definition of gmapT
411 newtype ID x = ID { unID :: x }
414 -- | The constant type constructor needed for the definition of gmapQl
415 newtype CONST c a = CONST { unCONST :: c }
418 -- | Type constructor for adding counters to queries
419 data Qi q a = Qi Int (Maybe q)
422 -- | The type constructor used in definition of gmapQr
423 newtype Qr r a = Qr { unQr :: r -> r }
426 -- | The type constructor used in definition of gmapMp
427 newtype Mp m x = Mp { unMp :: m (x, Bool) }
431 ------------------------------------------------------------------------------
435 ------------------------------------------------------------------------------
438 -- | Build a term skeleton
439 fromConstr :: Data a => Constr -> a
440 fromConstr = fromConstrB (error "Data.Data.fromConstr")
443 -- | Build a term and use a generic function for subterms
444 fromConstrB :: Data a
445 => (forall d. Data d => d)
448 fromConstrB f = unID . gunfold k z
454 -- | Monadic variation on 'fromConstrB'
455 fromConstrM :: (Monad m, Data a)
456 => (forall d. Data d => m d)
459 fromConstrM f = gunfold k z
461 k c = do { c' <- c; b <- f; return (c' b) }
466 ------------------------------------------------------------------------------
468 -- Datatype and constructor representations
470 ------------------------------------------------------------------------------
474 -- | Representation of datatypes.
475 -- A package of constructor representations with names of type and module.
477 data DataType = DataType
485 -- | Representation of constructors
487 { conrep :: ConstrRep
488 , constring :: String
489 , confields :: [String] -- for AlgRep only
490 , confixity :: Fixity -- for AlgRep only
491 , datatype :: DataType
494 instance Show Constr where
498 -- | Equality of constructors
499 instance Eq Constr where
500 c == c' = constrRep c == constrRep c'
503 -- | Public representation of datatypes
504 data DataRep = AlgRep [Constr]
511 -- The list of constructors could be an array, a balanced tree, or others.
514 -- | Public representation of constructors
515 data ConstrRep = AlgConstr ConIndex
517 | FloatConstr Rational
523 -- | Unique index for datatype constructors,
524 -- counting from 1 in the order they are given in the program text.
528 -- | Fixity of constructors
530 | Infix -- Later: add associativity and precedence
535 ------------------------------------------------------------------------------
537 -- Observers for datatype representations
539 ------------------------------------------------------------------------------
542 -- | Gets the type constructor including the module
543 dataTypeName :: DataType -> String
548 -- | Gets the public presentation of a datatype
549 dataTypeRep :: DataType -> DataRep
550 dataTypeRep = datarep
553 -- | Gets the datatype of a constructor
554 constrType :: Constr -> DataType
555 constrType = datatype
558 -- | Gets the public presentation of constructors
559 constrRep :: Constr -> ConstrRep
563 -- | Look up a constructor by its representation
564 repConstr :: DataType -> ConstrRep -> Constr
566 case (dataTypeRep dt, cr) of
567 (AlgRep cs, AlgConstr i) -> cs !! (i-1)
568 (IntRep, IntConstr i) -> mkIntConstr dt i
569 (FloatRep, FloatConstr f) -> mkRealConstr dt f
570 (CharRep, CharConstr c) -> mkCharConstr dt c
571 _ -> error "repConstr"
575 ------------------------------------------------------------------------------
577 -- Representations of algebraic data types
579 ------------------------------------------------------------------------------
582 -- | Constructs an algebraic datatype
583 mkDataType :: String -> [Constr] -> DataType
584 mkDataType str cs = DataType
586 , datarep = AlgRep cs
590 -- | Constructs a constructor
591 mkConstr :: DataType -> String -> [String] -> Fixity -> Constr
592 mkConstr dt str fields fix =
594 { conrep = AlgConstr idx
601 idx = head [ i | (c,i) <- dataTypeConstrs dt `zip` [1..],
602 showConstr c == str ]
605 -- | Gets the constructors of an algebraic datatype
606 dataTypeConstrs :: DataType -> [Constr]
607 dataTypeConstrs dt = case datarep dt of
608 (AlgRep cons) -> cons
609 _ -> error "dataTypeConstrs"
612 -- | Gets the field labels of a constructor. The list of labels
613 -- is returned in the same order as they were given in the original
614 -- constructor declaration.
615 constrFields :: Constr -> [String]
616 constrFields = confields
619 -- | Gets the fixity of a constructor
620 constrFixity :: Constr -> Fixity
621 constrFixity = confixity
625 ------------------------------------------------------------------------------
627 -- From strings to constr's and vice versa: all data types
629 ------------------------------------------------------------------------------
632 -- | Gets the string for a constructor
633 showConstr :: Constr -> String
634 showConstr = constring
637 -- | Lookup a constructor via a string
638 readConstr :: DataType -> String -> Maybe Constr
640 case dataTypeRep dt of
641 AlgRep cons -> idx cons
642 IntRep -> mkReadCon (\i -> (mkPrimCon dt str (IntConstr i)))
643 FloatRep -> mkReadCon (\f -> (mkPrimCon dt str (FloatConstr f)))
644 CharRep -> mkReadCon (\c -> (mkPrimCon dt str (CharConstr c)))
648 -- Read a value and build a constructor
649 mkReadCon :: Read t => (t -> Constr) -> Maybe Constr
650 mkReadCon f = case (reads str) of
651 [(t,"")] -> Just (f t)
654 -- Traverse list of algebraic datatype constructors
655 idx :: [Constr] -> Maybe Constr
656 idx cons = let fit = filter ((==) str . showConstr) cons
662 ------------------------------------------------------------------------------
664 -- Convenience funtions: algebraic data types
666 ------------------------------------------------------------------------------
669 -- | Test for an algebraic type
670 isAlgType :: DataType -> Bool
671 isAlgType dt = case datarep dt of
676 -- | Gets the constructor for an index (algebraic datatypes only)
677 indexConstr :: DataType -> ConIndex -> Constr
678 indexConstr dt idx = case datarep dt of
679 (AlgRep cs) -> cs !! (idx-1)
680 _ -> error "indexConstr"
683 -- | Gets the index of a constructor (algebraic datatypes only)
684 constrIndex :: Constr -> ConIndex
685 constrIndex con = case constrRep con of
686 (AlgConstr idx) -> idx
687 _ -> error "constrIndex"
690 -- | Gets the maximum constructor index of an algebraic datatype
691 maxConstrIndex :: DataType -> ConIndex
692 maxConstrIndex dt = case dataTypeRep dt of
693 AlgRep cs -> length cs
694 _ -> error "maxConstrIndex"
698 ------------------------------------------------------------------------------
700 -- Representation of primitive types
702 ------------------------------------------------------------------------------
705 -- | Constructs the 'Int' type
706 mkIntType :: String -> DataType
707 mkIntType = mkPrimType IntRep
710 -- | Constructs the 'Float' type
711 mkFloatType :: String -> DataType
712 mkFloatType = mkPrimType FloatRep
715 -- | This function is now deprecated. Please use 'mkCharType' instead.
716 {-# DEPRECATED mkStringType "Use mkCharType instead" #-}
717 mkStringType :: String -> DataType
718 mkStringType = mkCharType
720 -- | Constructs the 'Char' type
721 mkCharType :: String -> DataType
722 mkCharType = mkPrimType CharRep
725 -- | Helper for 'mkIntType', 'mkFloatType', 'mkStringType'
726 mkPrimType :: DataRep -> String -> DataType
727 mkPrimType dr str = DataType
733 -- Makes a constructor for primitive types
734 mkPrimCon :: DataType -> String -> ConstrRep -> Constr
735 mkPrimCon dt str cr = Constr
739 , confields = error "constrFields"
740 , confixity = error "constrFixity"
743 -- | This function is now deprecated. Please use 'mkIntegralConstr' instead.
744 {-# DEPRECATED mkIntConstr "Use mkIntegralConstr instead" #-}
745 mkIntConstr :: DataType -> Integer -> Constr
746 mkIntConstr = mkIntegralConstr
748 mkIntegralConstr :: (Integral a) => DataType -> a -> Constr
749 mkIntegralConstr dt i = case datarep dt of
750 IntRep -> mkPrimCon dt (show i) (IntConstr (toInteger i))
751 _ -> error "mkIntegralConstr"
753 -- | This function is now deprecated. Please use 'mkRealConstr' instead.
754 {-# DEPRECATED mkFloatConstr "Use mkRealConstr instead" #-}
755 mkFloatConstr :: DataType -> Double -> Constr
756 mkFloatConstr dt = mkRealConstr dt . toRational
758 mkRealConstr :: (Real a) => DataType -> a -> Constr
759 mkRealConstr dt f = case datarep dt of
760 FloatRep -> mkPrimCon dt (show f) (FloatConstr (toRational f))
761 _ -> error "mkRealConstr"
763 -- | This function is now deprecated. Please use 'mkCharConstr' instead.
764 {-# DEPRECATED mkStringConstr "Use mkCharConstr instead" #-}
765 mkStringConstr :: DataType -> String -> Constr
766 mkStringConstr dt str =
768 CharRep -> case str of
769 [c] -> mkPrimCon dt (show c) (CharConstr c)
770 _ -> error "mkStringConstr: input String must contain a single character"
771 _ -> error "mkStringConstr"
773 -- | Makes a constructor for 'Char'.
774 mkCharConstr :: DataType -> Char -> Constr
775 mkCharConstr dt c = case datarep dt of
776 CharRep -> mkPrimCon dt (show c) (CharConstr c)
777 _ -> error "mkCharConstr"
780 ------------------------------------------------------------------------------
782 -- Non-representations for non-presentable types
784 ------------------------------------------------------------------------------
787 -- | Deprecated version (misnamed)
788 {-# DEPRECATED mkNorepType "Use mkNoRepType instead" #-}
789 mkNorepType :: String -> DataType
790 mkNorepType str = DataType
795 -- | Constructs a non-representation for a non-presentable type
796 mkNoRepType :: String -> DataType
797 mkNoRepType str = DataType
802 -- | Test for a non-representable type
803 isNorepType :: DataType -> Bool
804 isNorepType dt = case datarep dt of
810 ------------------------------------------------------------------------------
812 -- Convenience for qualified type constructors
814 ------------------------------------------------------------------------------
817 -- | Gets the unqualified type constructor:
818 -- drop *.*.*... before name
820 tyconUQname :: String -> String
821 tyconUQname x = let x' = dropWhile (not . (==) '.') x
822 in if x' == [] then x else tyconUQname (tail x')
825 -- | Gets the module of a type constructor:
826 -- take *.*.*... before name
827 tyconModule :: String -> String
828 tyconModule x = let (a,b) = break ((==) '.') x
831 else a ++ tyconModule' (tail b)
833 tyconModule' y = let y' = tyconModule y
834 in if y' == "" then "" else ('.':y')
839 ------------------------------------------------------------------------------
840 ------------------------------------------------------------------------------
842 -- Instances of the Data class for Prelude-like types.
843 -- We define top-level definitions for representations.
845 ------------------------------------------------------------------------------
848 falseConstr :: Constr
849 falseConstr = mkConstr boolDataType "False" [] Prefix
851 trueConstr = mkConstr boolDataType "True" [] Prefix
853 boolDataType :: DataType
854 boolDataType = mkDataType "Prelude.Bool" [falseConstr,trueConstr]
856 instance Data Bool where
857 toConstr False = falseConstr
858 toConstr True = trueConstr
859 gunfold _ z c = case constrIndex c of
863 dataTypeOf _ = boolDataType
866 ------------------------------------------------------------------------------
869 charType = mkCharType "Prelude.Char"
871 instance Data Char where
872 toConstr x = mkCharConstr charType x
873 gunfold _ z c = case constrRep c of
874 (CharConstr x) -> z x
876 dataTypeOf _ = charType
879 ------------------------------------------------------------------------------
881 floatType :: DataType
882 floatType = mkFloatType "Prelude.Float"
884 instance Data Float where
885 toConstr = mkRealConstr floatType
886 gunfold _ z c = case constrRep c of
887 (FloatConstr x) -> z (realToFrac x)
889 dataTypeOf _ = floatType
892 ------------------------------------------------------------------------------
894 doubleType :: DataType
895 doubleType = mkFloatType "Prelude.Double"
897 instance Data Double where
898 toConstr = mkRealConstr doubleType
899 gunfold _ z c = case constrRep c of
900 (FloatConstr x) -> z (realToFrac x)
902 dataTypeOf _ = doubleType
905 ------------------------------------------------------------------------------
908 intType = mkIntType "Prelude.Int"
910 instance Data Int where
911 toConstr x = mkIntConstr intType (fromIntegral x)
912 gunfold _ z c = case constrRep c of
913 (IntConstr x) -> z (fromIntegral x)
915 dataTypeOf _ = intType
918 ------------------------------------------------------------------------------
920 integerType :: DataType
921 integerType = mkIntType "Prelude.Integer"
923 instance Data Integer where
924 toConstr = mkIntConstr integerType
925 gunfold _ z c = case constrRep c of
928 dataTypeOf _ = integerType
931 ------------------------------------------------------------------------------
934 int8Type = mkIntType "Data.Int.Int8"
936 instance Data Int8 where
937 toConstr x = mkIntConstr int8Type (fromIntegral x)
938 gunfold _ z c = case constrRep c of
939 (IntConstr x) -> z (fromIntegral x)
941 dataTypeOf _ = int8Type
944 ------------------------------------------------------------------------------
946 int16Type :: DataType
947 int16Type = mkIntType "Data.Int.Int16"
949 instance Data Int16 where
950 toConstr x = mkIntConstr int16Type (fromIntegral x)
951 gunfold _ z c = case constrRep c of
952 (IntConstr x) -> z (fromIntegral x)
954 dataTypeOf _ = int16Type
957 ------------------------------------------------------------------------------
959 int32Type :: DataType
960 int32Type = mkIntType "Data.Int.Int32"
962 instance Data Int32 where
963 toConstr x = mkIntConstr int32Type (fromIntegral x)
964 gunfold _ z c = case constrRep c of
965 (IntConstr x) -> z (fromIntegral x)
967 dataTypeOf _ = int32Type
970 ------------------------------------------------------------------------------
972 int64Type :: DataType
973 int64Type = mkIntType "Data.Int.Int64"
975 instance Data Int64 where
976 toConstr x = mkIntConstr int64Type (fromIntegral x)
977 gunfold _ z c = case constrRep c of
978 (IntConstr x) -> z (fromIntegral x)
980 dataTypeOf _ = int64Type
983 ------------------------------------------------------------------------------
986 wordType = mkIntType "Data.Word.Word"
988 instance Data Word where
989 toConstr x = mkIntConstr wordType (fromIntegral x)
990 gunfold _ z c = case constrRep c of
991 (IntConstr x) -> z (fromIntegral x)
993 dataTypeOf _ = wordType
996 ------------------------------------------------------------------------------
998 word8Type :: DataType
999 word8Type = mkIntType "Data.Word.Word8"
1001 instance Data Word8 where
1002 toConstr x = mkIntConstr word8Type (fromIntegral x)
1003 gunfold _ z c = case constrRep c of
1004 (IntConstr x) -> z (fromIntegral x)
1005 _ -> error "gunfold"
1006 dataTypeOf _ = word8Type
1009 ------------------------------------------------------------------------------
1011 word16Type :: DataType
1012 word16Type = mkIntType "Data.Word.Word16"
1014 instance Data Word16 where
1015 toConstr x = mkIntConstr word16Type (fromIntegral x)
1016 gunfold _ z c = case constrRep c of
1017 (IntConstr x) -> z (fromIntegral x)
1018 _ -> error "gunfold"
1019 dataTypeOf _ = word16Type
1022 ------------------------------------------------------------------------------
1024 word32Type :: DataType
1025 word32Type = mkIntType "Data.Word.Word32"
1027 instance Data Word32 where
1028 toConstr x = mkIntConstr word32Type (fromIntegral x)
1029 gunfold _ z c = case constrRep c of
1030 (IntConstr x) -> z (fromIntegral x)
1031 _ -> error "gunfold"
1032 dataTypeOf _ = word32Type
1035 ------------------------------------------------------------------------------
1037 word64Type :: DataType
1038 word64Type = mkIntType "Data.Word.Word64"
1040 instance Data Word64 where
1041 toConstr x = mkIntConstr word64Type (fromIntegral x)
1042 gunfold _ z c = case constrRep c of
1043 (IntConstr x) -> z (fromIntegral x)
1044 _ -> error "gunfold"
1045 dataTypeOf _ = word64Type
1048 ------------------------------------------------------------------------------
1050 ratioConstr :: Constr
1051 ratioConstr = mkConstr ratioDataType ":%" [] Infix
1053 ratioDataType :: DataType
1054 ratioDataType = mkDataType "GHC.Real.Ratio" [ratioConstr]
1056 instance (Data a, Integral a) => Data (Ratio a) where
1057 gfoldl k z (a :% b) = z (:%) `k` a `k` b
1058 toConstr _ = ratioConstr
1059 gunfold k z c | constrIndex c == 1 = k (k (z (:%)))
1060 gunfold _ _ _ = error "gunfold"
1061 dataTypeOf _ = ratioDataType
1064 ------------------------------------------------------------------------------
1067 nilConstr = mkConstr listDataType "[]" [] Prefix
1068 consConstr :: Constr
1069 consConstr = mkConstr listDataType "(:)" [] Infix
1071 listDataType :: DataType
1072 listDataType = mkDataType "Prelude.[]" [nilConstr,consConstr]
1074 instance Data a => Data [a] where
1075 gfoldl _ z [] = z []
1076 gfoldl f z (x:xs) = z (:) `f` x `f` xs
1077 toConstr [] = nilConstr
1078 toConstr (_:_) = consConstr
1079 gunfold k z c = case constrIndex c of
1082 _ -> error "gunfold"
1083 dataTypeOf _ = listDataType
1084 dataCast1 f = gcast1 f
1087 -- The gmaps are given as an illustration.
1088 -- This shows that the gmaps for lists are different from list maps.
1091 gmapT f (x:xs) = (f x:f xs)
1093 gmapQ f (x:xs) = [f x,f xs]
1094 gmapM _ [] = return []
1095 gmapM f (x:xs) = f x >>= \x' -> f xs >>= \xs' -> return (x':xs')
1098 ------------------------------------------------------------------------------
1100 nothingConstr :: Constr
1101 nothingConstr = mkConstr maybeDataType "Nothing" [] Prefix
1102 justConstr :: Constr
1103 justConstr = mkConstr maybeDataType "Just" [] Prefix
1105 maybeDataType :: DataType
1106 maybeDataType = mkDataType "Prelude.Maybe" [nothingConstr,justConstr]
1108 instance Data a => Data (Maybe a) where
1109 gfoldl _ z Nothing = z Nothing
1110 gfoldl f z (Just x) = z Just `f` x
1111 toConstr Nothing = nothingConstr
1112 toConstr (Just _) = justConstr
1113 gunfold k z c = case constrIndex c of
1116 _ -> error "gunfold"
1117 dataTypeOf _ = maybeDataType
1118 dataCast1 f = gcast1 f
1121 ------------------------------------------------------------------------------
1124 ltConstr = mkConstr orderingDataType "LT" [] Prefix
1126 eqConstr = mkConstr orderingDataType "EQ" [] Prefix
1128 gtConstr = mkConstr orderingDataType "GT" [] Prefix
1130 orderingDataType :: DataType
1131 orderingDataType = mkDataType "Prelude.Ordering" [ltConstr,eqConstr,gtConstr]
1133 instance Data Ordering where
1134 gfoldl _ z LT = z LT
1135 gfoldl _ z EQ = z EQ
1136 gfoldl _ z GT = z GT
1137 toConstr LT = ltConstr
1138 toConstr EQ = eqConstr
1139 toConstr GT = gtConstr
1140 gunfold _ z c = case constrIndex c of
1144 _ -> error "gunfold"
1145 dataTypeOf _ = orderingDataType
1148 ------------------------------------------------------------------------------
1150 leftConstr :: Constr
1151 leftConstr = mkConstr eitherDataType "Left" [] Prefix
1153 rightConstr :: Constr
1154 rightConstr = mkConstr eitherDataType "Right" [] Prefix
1156 eitherDataType :: DataType
1157 eitherDataType = mkDataType "Prelude.Either" [leftConstr,rightConstr]
1159 instance (Data a, Data b) => Data (Either a b) where
1160 gfoldl f z (Left a) = z Left `f` a
1161 gfoldl f z (Right a) = z Right `f` a
1162 toConstr (Left _) = leftConstr
1163 toConstr (Right _) = rightConstr
1164 gunfold k z c = case constrIndex c of
1167 _ -> error "gunfold"
1168 dataTypeOf _ = eitherDataType
1169 dataCast2 f = gcast2 f
1172 ------------------------------------------------------------------------------
1174 tuple0Constr :: Constr
1175 tuple0Constr = mkConstr tuple0DataType "()" [] Prefix
1177 tuple0DataType :: DataType
1178 tuple0DataType = mkDataType "Prelude.()" [tuple0Constr]
1180 instance Data () where
1181 toConstr () = tuple0Constr
1182 gunfold _ z c | constrIndex c == 1 = z ()
1183 gunfold _ _ _ = error "gunfold"
1184 dataTypeOf _ = tuple0DataType
1187 ------------------------------------------------------------------------------
1189 tuple2Constr :: Constr
1190 tuple2Constr = mkConstr tuple2DataType "(,)" [] Infix
1192 tuple2DataType :: DataType
1193 tuple2DataType = mkDataType "Prelude.(,)" [tuple2Constr]
1195 instance (Data a, Data b) => Data (a,b) where
1196 gfoldl f z (a,b) = z (,) `f` a `f` b
1197 toConstr (_,_) = tuple2Constr
1198 gunfold k z c | constrIndex c == 1 = k (k (z (,)))
1199 gunfold _ _ _ = error "gunfold"
1200 dataTypeOf _ = tuple2DataType
1201 dataCast2 f = gcast2 f
1204 ------------------------------------------------------------------------------
1206 tuple3Constr :: Constr
1207 tuple3Constr = mkConstr tuple3DataType "(,,)" [] Infix
1209 tuple3DataType :: DataType
1210 tuple3DataType = mkDataType "Prelude.(,,)" [tuple3Constr]
1212 instance (Data a, Data b, Data c) => Data (a,b,c) where
1213 gfoldl f z (a,b,c) = z (,,) `f` a `f` b `f` c
1214 toConstr (_,_,_) = tuple3Constr
1215 gunfold k z c | constrIndex c == 1 = k (k (k (z (,,))))
1216 gunfold _ _ _ = error "gunfold"
1217 dataTypeOf _ = tuple3DataType
1220 ------------------------------------------------------------------------------
1222 tuple4Constr :: Constr
1223 tuple4Constr = mkConstr tuple4DataType "(,,,)" [] Infix
1225 tuple4DataType :: DataType
1226 tuple4DataType = mkDataType "Prelude.(,,,)" [tuple4Constr]
1228 instance (Data a, Data b, Data c, Data d)
1229 => Data (a,b,c,d) where
1230 gfoldl f z (a,b,c,d) = z (,,,) `f` a `f` b `f` c `f` d
1231 toConstr (_,_,_,_) = tuple4Constr
1232 gunfold k z c = case constrIndex c of
1233 1 -> k (k (k (k (z (,,,)))))
1234 _ -> error "gunfold"
1235 dataTypeOf _ = tuple4DataType
1238 ------------------------------------------------------------------------------
1240 tuple5Constr :: Constr
1241 tuple5Constr = mkConstr tuple5DataType "(,,,,)" [] Infix
1243 tuple5DataType :: DataType
1244 tuple5DataType = mkDataType "Prelude.(,,,,)" [tuple5Constr]
1246 instance (Data a, Data b, Data c, Data d, Data e)
1247 => Data (a,b,c,d,e) where
1248 gfoldl f z (a,b,c,d,e) = z (,,,,) `f` a `f` b `f` c `f` d `f` e
1249 toConstr (_,_,_,_,_) = tuple5Constr
1250 gunfold k z c = case constrIndex c of
1251 1 -> k (k (k (k (k (z (,,,,))))))
1252 _ -> error "gunfold"
1253 dataTypeOf _ = tuple5DataType
1256 ------------------------------------------------------------------------------
1258 tuple6Constr :: Constr
1259 tuple6Constr = mkConstr tuple6DataType "(,,,,,)" [] Infix
1261 tuple6DataType :: DataType
1262 tuple6DataType = mkDataType "Prelude.(,,,,,)" [tuple6Constr]
1264 instance (Data a, Data b, Data c, Data d, Data e, Data f)
1265 => Data (a,b,c,d,e,f) where
1266 gfoldl f z (a,b,c,d,e,f') = z (,,,,,) `f` a `f` b `f` c `f` d `f` e `f` f'
1267 toConstr (_,_,_,_,_,_) = tuple6Constr
1268 gunfold k z c = case constrIndex c of
1269 1 -> k (k (k (k (k (k (z (,,,,,)))))))
1270 _ -> error "gunfold"
1271 dataTypeOf _ = tuple6DataType
1274 ------------------------------------------------------------------------------
1276 tuple7Constr :: Constr
1277 tuple7Constr = mkConstr tuple7DataType "(,,,,,,)" [] Infix
1279 tuple7DataType :: DataType
1280 tuple7DataType = mkDataType "Prelude.(,,,,,,)" [tuple7Constr]
1282 instance (Data a, Data b, Data c, Data d, Data e, Data f, Data g)
1283 => Data (a,b,c,d,e,f,g) where
1284 gfoldl f z (a,b,c,d,e,f',g) =
1285 z (,,,,,,) `f` a `f` b `f` c `f` d `f` e `f` f' `f` g
1286 toConstr (_,_,_,_,_,_,_) = tuple7Constr
1287 gunfold k z c = case constrIndex c of
1288 1 -> k (k (k (k (k (k (k (z (,,,,,,))))))))
1289 _ -> error "gunfold"
1290 dataTypeOf _ = tuple7DataType
1293 ------------------------------------------------------------------------------
1295 instance Typeable a => Data (Ptr a) where
1296 toConstr _ = error "toConstr"
1297 gunfold _ _ = error "gunfold"
1298 dataTypeOf _ = mkNoRepType "GHC.Ptr.Ptr"
1301 ------------------------------------------------------------------------------
1303 instance Typeable a => Data (ForeignPtr a) where
1304 toConstr _ = error "toConstr"
1305 gunfold _ _ = error "gunfold"
1306 dataTypeOf _ = mkNoRepType "GHC.ForeignPtr.ForeignPtr"
1309 ------------------------------------------------------------------------------
1310 -- The Data instance for Array preserves data abstraction at the cost of
1311 -- inefficiency. We omit reflection services for the sake of data abstraction.
1312 instance (Typeable a, Data b, Ix a) => Data (Array a b)
1314 gfoldl f z a = z (listArray (bounds a)) `f` (elems a)
1315 toConstr _ = error "toConstr"
1316 gunfold _ _ = error "gunfold"
1317 dataTypeOf _ = mkNoRepType "Data.Array.Array"