1 {-# OPTIONS_GHC -XNoImplicitPrelude -XOverlappingInstances -funbox-strict-fields #-}
3 -- The -XOverlappingInstances flag allows the user to over-ride
4 -- the instances for Typeable given here. In particular, we provide an instance
5 -- instance ... => Typeable (s a)
6 -- But a user might want to say
7 -- instance ... => Typeable (MyType a b)
9 -----------------------------------------------------------------------------
11 -- Module : Data.Typeable
12 -- Copyright : (c) The University of Glasgow, CWI 2001--2004
13 -- License : BSD-style (see the file libraries/base/LICENSE)
15 -- Maintainer : libraries@haskell.org
16 -- Stability : experimental
17 -- Portability : portable
19 -- The 'Typeable' class reifies types to some extent by associating type
20 -- representations to types. These type representations can be compared,
21 -- and one can in turn define a type-safe cast operation. To this end,
22 -- an unsafe cast is guarded by a test for type (representation)
23 -- equivalence. The module "Data.Dynamic" uses Typeable for an
24 -- implementation of dynamics. The module "Data.Data" uses Typeable
25 -- and type-safe cast (but not dynamics) to support the \"Scrap your
26 -- boilerplate\" style of generic programming.
28 -----------------------------------------------------------------------------
33 -- * The Typeable class
34 Typeable( typeOf ), -- :: a -> TypeRep
37 cast, -- :: (Typeable a, Typeable b) => a -> Maybe b
38 gcast, -- a generalisation of cast
40 -- * Type representations
41 TypeRep, -- abstract, instance of: Eq, Show, Typeable
42 TyCon, -- abstract, instance of: Eq, Show, Typeable
45 -- * Construction of type representations
46 mkTyCon, -- :: String -> TyCon
47 mkTyConApp, -- :: TyCon -> [TypeRep] -> TypeRep
48 mkAppTy, -- :: TypeRep -> TypeRep -> TypeRep
49 mkFunTy, -- :: TypeRep -> TypeRep -> TypeRep
51 -- * Observation of type representations
52 splitTyConApp, -- :: TypeRep -> (TyCon, [TypeRep])
53 funResultTy, -- :: TypeRep -> TypeRep -> Maybe TypeRep
54 typeRepTyCon, -- :: TypeRep -> TyCon
55 typeRepArgs, -- :: TypeRep -> [TypeRep]
56 tyConString, -- :: TyCon -> String
57 typeRepKey, -- :: TypeRep -> IO Int
59 -- * The other Typeable classes
60 -- | /Note:/ The general instances are provided for GHC only.
61 Typeable1( typeOf1 ), -- :: t a -> TypeRep
62 Typeable2( typeOf2 ), -- :: t a b -> TypeRep
63 Typeable3( typeOf3 ), -- :: t a b c -> TypeRep
64 Typeable4( typeOf4 ), -- :: t a b c d -> TypeRep
65 Typeable5( typeOf5 ), -- :: t a b c d e -> TypeRep
66 Typeable6( typeOf6 ), -- :: t a b c d e f -> TypeRep
67 Typeable7( typeOf7 ), -- :: t a b c d e f g -> TypeRep
68 gcast1, -- :: ... => c (t a) -> Maybe (c (t' a))
69 gcast2, -- :: ... => c (t a b) -> Maybe (c (t' a b))
71 -- * Default instances
72 -- | /Note:/ These are not needed by GHC, for which these instances
73 -- are generated by general instance declarations.
74 typeOfDefault, -- :: (Typeable1 t, Typeable a) => t a -> TypeRep
75 typeOf1Default, -- :: (Typeable2 t, Typeable a) => t a b -> TypeRep
76 typeOf2Default, -- :: (Typeable3 t, Typeable a) => t a b c -> TypeRep
77 typeOf3Default, -- :: (Typeable4 t, Typeable a) => t a b c d -> TypeRep
78 typeOf4Default, -- :: (Typeable5 t, Typeable a) => t a b c d e -> TypeRep
79 typeOf5Default, -- :: (Typeable6 t, Typeable a) => t a b c d e f -> TypeRep
80 typeOf6Default -- :: (Typeable7 t, Typeable a) => t a b c d e f g -> TypeRep
84 import qualified Data.HashTable as HT
88 import Data.List( foldl, intersperse )
91 #ifdef __GLASGOW_HASKELL__
93 import GHC.Show (Show(..), ShowS,
94 shows, showString, showChar, showParen)
95 import GHC.Err (undefined)
96 import GHC.Num (Integer, fromInteger, (+))
97 import GHC.Real ( rem, Ratio )
98 import GHC.IORef (IORef,newIORef)
99 import GHC.IO (unsafePerformIO,block)
101 -- These imports are so we can define Typeable instances
102 -- It'd be better to give Typeable instances in the modules themselves
103 -- but they all have to be compiled before Typeable
107 import GHC.STRef ( STRef )
108 import GHC.Ptr ( Ptr, FunPtr )
109 import GHC.Stable ( StablePtr, newStablePtr, freeStablePtr,
110 deRefStablePtr, castStablePtrToPtr,
112 import GHC.Arr ( Array, STArray )
117 import Hugs.Prelude ( Key(..), TypeRep(..), TyCon(..), Ratio,
118 Handle, Ptr, FunPtr, ForeignPtr, StablePtr )
119 import Hugs.IORef ( IORef, newIORef, readIORef, writeIORef )
120 import Hugs.IOExts ( unsafePerformIO )
121 -- For the Typeable instance
122 import Hugs.Array ( Array )
124 import Hugs.ConcBase ( MVar )
128 import NHC.IOExtras (IOArray,IORef,newIORef,readIORef,writeIORef,unsafePerformIO)
131 -- For the Typeable instance
132 import NHC.FFI ( Ptr,FunPtr,StablePtr,ForeignPtr )
133 import Array ( Array )
136 #include "Typeable.h"
140 -------------------------------------------------------------
142 -- Type representations
144 -------------------------------------------------------------
146 -- | A concrete representation of a (monomorphic) type. 'TypeRep'
147 -- supports reasonably efficient equality.
148 data TypeRep = TypeRep !Key TyCon [TypeRep]
150 -- Compare keys for equality
151 instance Eq TypeRep where
152 (TypeRep k1 _ _) == (TypeRep k2 _ _) = k1 == k2
154 -- | An abstract representation of a type constructor. 'TyCon' objects can
155 -- be built using 'mkTyCon'.
156 data TyCon = TyCon !Key String
158 instance Eq TyCon where
159 (TyCon t1 _) == (TyCon t2 _) = t1 == t2
162 -- | Returns a unique integer associated with a 'TypeRep'. This can
163 -- be used for making a mapping with TypeReps
164 -- as the keys, for example. It is guaranteed that @t1 == t2@ if and only if
165 -- @typeRepKey t1 == typeRepKey t2@.
167 -- It is in the 'IO' monad because the actual value of the key may
168 -- vary from run to run of the program. You should only rely on
169 -- the equality property, not any actual key value. The relative ordering
170 -- of keys has no meaning either.
172 typeRepKey :: TypeRep -> IO Int
173 typeRepKey (TypeRep (Key i) _ _) = return i
176 -- let fTy = mkTyCon "Foo" in show (mkTyConApp (mkTyCon ",,")
179 -- returns "(Foo,Foo,Foo)"
181 -- The TypeRep Show instance promises to print tuple types
182 -- correctly. Tuple type constructors are specified by a
183 -- sequence of commas, e.g., (mkTyCon ",,,,") returns
184 -- the 5-tuple tycon.
186 ----------------- Construction --------------------
188 -- | Applies a type constructor to a sequence of types
189 mkTyConApp :: TyCon -> [TypeRep] -> TypeRep
190 mkTyConApp tc@(TyCon tc_k _) args
191 = TypeRep (appKeys tc_k arg_ks) tc args
193 arg_ks = [k | TypeRep k _ _ <- args]
195 -- | A special case of 'mkTyConApp', which applies the function
196 -- type constructor to a pair of types.
197 mkFunTy :: TypeRep -> TypeRep -> TypeRep
198 mkFunTy f a = mkTyConApp funTc [f,a]
200 -- | Splits a type constructor application
201 splitTyConApp :: TypeRep -> (TyCon,[TypeRep])
202 splitTyConApp (TypeRep _ tc trs) = (tc,trs)
204 -- | Applies a type to a function type. Returns: @'Just' u@ if the
205 -- first argument represents a function of type @t -> u@ and the
206 -- second argument represents a function of type @t@. Otherwise,
207 -- returns 'Nothing'.
208 funResultTy :: TypeRep -> TypeRep -> Maybe TypeRep
209 funResultTy trFun trArg
210 = case splitTyConApp trFun of
211 (tc, [t1,t2]) | tc == funTc && t1 == trArg -> Just t2
214 -- | Adds a TypeRep argument to a TypeRep.
215 mkAppTy :: TypeRep -> TypeRep -> TypeRep
216 mkAppTy (TypeRep tr_k tc trs) arg_tr
217 = let (TypeRep arg_k _ _) = arg_tr
218 in TypeRep (appKey tr_k arg_k) tc (trs++[arg_tr])
220 -- If we enforce the restriction that there is only one
221 -- @TyCon@ for a type & it is shared among all its uses,
222 -- we can map them onto Ints very simply. The benefit is,
223 -- of course, that @TyCon@s can then be compared efficiently.
225 -- Provided the implementor of other @Typeable@ instances
226 -- takes care of making all the @TyCon@s CAFs (toplevel constants),
229 -- If this constraint does turn out to be a sore thumb, changing
230 -- the Eq instance for TyCons is trivial.
232 -- | Builds a 'TyCon' object representing a type constructor. An
233 -- implementation of "Data.Typeable" should ensure that the following holds:
235 -- > mkTyCon "a" == mkTyCon "a"
238 mkTyCon :: String -- ^ the name of the type constructor (should be unique
239 -- in the program, so it might be wise to use the
240 -- fully qualified name).
241 -> TyCon -- ^ A unique 'TyCon' object
242 mkTyCon str = TyCon (mkTyConKey str) str
244 ----------------- Observation ---------------------
246 -- | Observe the type constructor of a type representation
247 typeRepTyCon :: TypeRep -> TyCon
248 typeRepTyCon (TypeRep _ tc _) = tc
250 -- | Observe the argument types of a type representation
251 typeRepArgs :: TypeRep -> [TypeRep]
252 typeRepArgs (TypeRep _ _ args) = args
254 -- | Observe string encoding of a type representation
255 tyConString :: TyCon -> String
256 tyConString (TyCon _ str) = str
258 ----------------- Showing TypeReps --------------------
260 instance Show TypeRep where
261 showsPrec p (TypeRep _ tycon tys) =
263 [] -> showsPrec p tycon
264 [x] | tycon == listTc -> showChar '[' . shows x . showChar ']'
265 [a,r] | tycon == funTc -> showParen (p > 8) $
269 xs | isTupleTyCon tycon -> showTuple xs
276 showsTypeRep :: TypeRep -> ShowS
279 instance Show TyCon where
280 showsPrec _ (TyCon _ s) = showString s
282 isTupleTyCon :: TyCon -> Bool
283 isTupleTyCon (TyCon _ ('(':',':_)) = True
284 isTupleTyCon _ = False
286 -- Some (Show.TypeRep) helpers:
288 showArgs :: Show a => [a] -> ShowS
290 showArgs [a] = showsPrec 10 a
291 showArgs (a:as) = showsPrec 10 a . showString " " . showArgs as
293 showTuple :: [TypeRep] -> ShowS
294 showTuple args = showChar '('
295 . (foldr (.) id $ intersperse (showChar ',')
296 $ map (showsPrec 10) args)
299 -------------------------------------------------------------
301 -- The Typeable class and friends
303 -------------------------------------------------------------
305 -- | The class 'Typeable' allows a concrete representation of a type to
307 class Typeable a where
308 typeOf :: a -> TypeRep
309 -- ^ Takes a value of type @a@ and returns a concrete representation
310 -- of that type. The /value/ of the argument should be ignored by
311 -- any instance of 'Typeable', so that it is safe to pass 'undefined' as
314 -- | Variant for unary type constructors
315 class Typeable1 t where
316 typeOf1 :: t a -> TypeRep
318 -- | For defining a 'Typeable' instance from any 'Typeable1' instance.
319 typeOfDefault :: (Typeable1 t, Typeable a) => t a -> TypeRep
320 typeOfDefault x = typeOf1 x `mkAppTy` typeOf (argType x)
325 -- | Variant for binary type constructors
326 class Typeable2 t where
327 typeOf2 :: t a b -> TypeRep
329 -- | For defining a 'Typeable1' instance from any 'Typeable2' instance.
330 typeOf1Default :: (Typeable2 t, Typeable a) => t a b -> TypeRep
331 typeOf1Default x = typeOf2 x `mkAppTy` typeOf (argType x)
333 argType :: t a b -> a
336 -- | Variant for 3-ary type constructors
337 class Typeable3 t where
338 typeOf3 :: t a b c -> TypeRep
340 -- | For defining a 'Typeable2' instance from any 'Typeable3' instance.
341 typeOf2Default :: (Typeable3 t, Typeable a) => t a b c -> TypeRep
342 typeOf2Default x = typeOf3 x `mkAppTy` typeOf (argType x)
344 argType :: t a b c -> a
347 -- | Variant for 4-ary type constructors
348 class Typeable4 t where
349 typeOf4 :: t a b c d -> TypeRep
351 -- | For defining a 'Typeable3' instance from any 'Typeable4' instance.
352 typeOf3Default :: (Typeable4 t, Typeable a) => t a b c d -> TypeRep
353 typeOf3Default x = typeOf4 x `mkAppTy` typeOf (argType x)
355 argType :: t a b c d -> a
358 -- | Variant for 5-ary type constructors
359 class Typeable5 t where
360 typeOf5 :: t a b c d e -> TypeRep
362 -- | For defining a 'Typeable4' instance from any 'Typeable5' instance.
363 typeOf4Default :: (Typeable5 t, Typeable a) => t a b c d e -> TypeRep
364 typeOf4Default x = typeOf5 x `mkAppTy` typeOf (argType x)
366 argType :: t a b c d e -> a
369 -- | Variant for 6-ary type constructors
370 class Typeable6 t where
371 typeOf6 :: t a b c d e f -> TypeRep
373 -- | For defining a 'Typeable5' instance from any 'Typeable6' instance.
374 typeOf5Default :: (Typeable6 t, Typeable a) => t a b c d e f -> TypeRep
375 typeOf5Default x = typeOf6 x `mkAppTy` typeOf (argType x)
377 argType :: t a b c d e f -> a
380 -- | Variant for 7-ary type constructors
381 class Typeable7 t where
382 typeOf7 :: t a b c d e f g -> TypeRep
384 -- | For defining a 'Typeable6' instance from any 'Typeable7' instance.
385 typeOf6Default :: (Typeable7 t, Typeable a) => t a b c d e f g -> TypeRep
386 typeOf6Default x = typeOf7 x `mkAppTy` typeOf (argType x)
388 argType :: t a b c d e f g -> a
391 #ifdef __GLASGOW_HASKELL__
392 -- Given a @Typeable@/n/ instance for an /n/-ary type constructor,
393 -- define the instances for partial applications.
394 -- Programmers using non-GHC implementations must do this manually
395 -- for each type constructor.
396 -- (The INSTANCE_TYPEABLE/n/ macros in Typeable.h include this.)
398 -- | One Typeable instance for all Typeable1 instances
399 instance (Typeable1 s, Typeable a)
400 => Typeable (s a) where
401 typeOf = typeOfDefault
403 -- | One Typeable1 instance for all Typeable2 instances
404 instance (Typeable2 s, Typeable a)
405 => Typeable1 (s a) where
406 typeOf1 = typeOf1Default
408 -- | One Typeable2 instance for all Typeable3 instances
409 instance (Typeable3 s, Typeable a)
410 => Typeable2 (s a) where
411 typeOf2 = typeOf2Default
413 -- | One Typeable3 instance for all Typeable4 instances
414 instance (Typeable4 s, Typeable a)
415 => Typeable3 (s a) where
416 typeOf3 = typeOf3Default
418 -- | One Typeable4 instance for all Typeable5 instances
419 instance (Typeable5 s, Typeable a)
420 => Typeable4 (s a) where
421 typeOf4 = typeOf4Default
423 -- | One Typeable5 instance for all Typeable6 instances
424 instance (Typeable6 s, Typeable a)
425 => Typeable5 (s a) where
426 typeOf5 = typeOf5Default
428 -- | One Typeable6 instance for all Typeable7 instances
429 instance (Typeable7 s, Typeable a)
430 => Typeable6 (s a) where
431 typeOf6 = typeOf6Default
433 #endif /* __GLASGOW_HASKELL__ */
435 -------------------------------------------------------------
439 -------------------------------------------------------------
441 -- | The type-safe cast operation
442 cast :: (Typeable a, Typeable b) => a -> Maybe b
445 r = if typeOf x == typeOf (fromJust r)
446 then Just $ unsafeCoerce x
449 -- | A flexible variation parameterised in a type constructor
450 gcast :: (Typeable a, Typeable b) => c a -> Maybe (c b)
453 r = if typeOf (getArg x) == typeOf (getArg (fromJust r))
454 then Just $ unsafeCoerce x
460 gcast1 :: (Typeable1 t, Typeable1 t') => c (t a) -> Maybe (c (t' a))
463 r = if typeOf1 (getArg x) == typeOf1 (getArg (fromJust r))
464 then Just $ unsafeCoerce x
469 -- | Cast for * -> * -> *
470 gcast2 :: (Typeable2 t, Typeable2 t') => c (t a b) -> Maybe (c (t' a b))
473 r = if typeOf2 (getArg x) == typeOf2 (getArg (fromJust r))
474 then Just $ unsafeCoerce x
479 -------------------------------------------------------------
481 -- Instances of the Typeable classes for Prelude types
483 -------------------------------------------------------------
485 INSTANCE_TYPEABLE0((),unitTc,"()")
486 INSTANCE_TYPEABLE1([],listTc,"[]")
487 INSTANCE_TYPEABLE1(Maybe,maybeTc,"Maybe")
488 INSTANCE_TYPEABLE1(Ratio,ratioTc,"Ratio")
489 INSTANCE_TYPEABLE2((->),funTc,"->")
490 INSTANCE_TYPEABLE1(IO,ioTc,"IO")
492 #if defined(__GLASGOW_HASKELL__) || defined(__HUGS__)
493 -- Types defined in GHC.MVar
494 INSTANCE_TYPEABLE1(MVar,mvarTc,"MVar" )
497 INSTANCE_TYPEABLE2(Array,arrayTc,"Array")
498 INSTANCE_TYPEABLE2(IOArray,iOArrayTc,"IOArray")
500 #ifdef __GLASGOW_HASKELL__
501 -- Hugs has these too, but their Typeable<n> instances are defined
502 -- elsewhere to keep this module within Haskell 98.
503 -- This is important because every invocation of runhugs or ffihugs
504 -- uses this module via Data.Dynamic.
505 INSTANCE_TYPEABLE2(ST,stTc,"ST")
506 INSTANCE_TYPEABLE2(STRef,stRefTc,"STRef")
507 INSTANCE_TYPEABLE3(STArray,sTArrayTc,"STArray")
511 INSTANCE_TYPEABLE2((,),pairTc,"(,)")
512 INSTANCE_TYPEABLE3((,,),tup3Tc,"(,,)")
513 INSTANCE_TYPEABLE4((,,,),tup4Tc,"(,,,)")
514 INSTANCE_TYPEABLE5((,,,,),tup5Tc,"(,,,,)")
515 INSTANCE_TYPEABLE6((,,,,,),tup6Tc,"(,,,,,)")
516 INSTANCE_TYPEABLE7((,,,,,,),tup7Tc,"(,,,,,,)")
519 INSTANCE_TYPEABLE1(Ptr,ptrTc,"Ptr")
520 INSTANCE_TYPEABLE1(FunPtr,funPtrTc,"FunPtr")
521 #ifndef __GLASGOW_HASKELL__
522 INSTANCE_TYPEABLE1(ForeignPtr,foreignPtrTc,"ForeignPtr")
524 INSTANCE_TYPEABLE1(StablePtr,stablePtrTc,"StablePtr")
525 INSTANCE_TYPEABLE1(IORef,iORefTc,"IORef")
527 -------------------------------------------------------
529 -- Generate Typeable instances for standard datatypes
531 -------------------------------------------------------
533 INSTANCE_TYPEABLE0(Bool,boolTc,"Bool")
534 INSTANCE_TYPEABLE0(Char,charTc,"Char")
535 INSTANCE_TYPEABLE0(Float,floatTc,"Float")
536 INSTANCE_TYPEABLE0(Double,doubleTc,"Double")
537 INSTANCE_TYPEABLE0(Int,intTc,"Int")
539 INSTANCE_TYPEABLE0(Word,wordTc,"Word" )
541 INSTANCE_TYPEABLE0(Integer,integerTc,"Integer")
542 INSTANCE_TYPEABLE0(Ordering,orderingTc,"Ordering")
543 #ifndef __GLASGOW_HASKELL__
544 INSTANCE_TYPEABLE0(Handle,handleTc,"Handle")
547 INSTANCE_TYPEABLE0(Int8,int8Tc,"Int8")
548 INSTANCE_TYPEABLE0(Int16,int16Tc,"Int16")
549 INSTANCE_TYPEABLE0(Int32,int32Tc,"Int32")
550 INSTANCE_TYPEABLE0(Int64,int64Tc,"Int64")
552 INSTANCE_TYPEABLE0(Word8,word8Tc,"Word8" )
553 INSTANCE_TYPEABLE0(Word16,word16Tc,"Word16")
554 INSTANCE_TYPEABLE0(Word32,word32Tc,"Word32")
555 INSTANCE_TYPEABLE0(Word64,word64Tc,"Word64")
557 INSTANCE_TYPEABLE0(TyCon,tyconTc,"TyCon")
558 INSTANCE_TYPEABLE0(TypeRep,typeRepTc,"TypeRep")
560 #ifdef __GLASGOW_HASKELL__
561 INSTANCE_TYPEABLE0(RealWorld,realWorldTc,"RealWorld")
564 ---------------------------------------------
568 ---------------------------------------------
571 newtype Key = Key Int deriving( Eq )
574 data KeyPr = KeyPr !Key !Key deriving( Eq )
576 hashKP :: KeyPr -> Int32
577 hashKP (KeyPr (Key k1) (Key k2)) = (HT.hashInt k1 + HT.hashInt k2) `rem` HT.prime
579 data Cache = Cache { next_key :: !(IORef Key), -- Not used by GHC (calls genSym instead)
580 tc_tbl :: !(HT.HashTable String Key),
581 ap_tbl :: !(HT.HashTable KeyPr Key) }
583 {-# NOINLINE cache #-}
584 #ifdef __GLASGOW_HASKELL__
585 foreign import ccall unsafe "RtsTypeable.h getOrSetTypeableStore"
586 getOrSetTypeableStore :: Ptr a -> IO (Ptr a)
590 cache = unsafePerformIO $ do
591 empty_tc_tbl <- HT.new (==) HT.hashString
592 empty_ap_tbl <- HT.new (==) hashKP
593 key_loc <- newIORef (Key 1)
594 let ret = Cache { next_key = key_loc,
595 tc_tbl = empty_tc_tbl,
596 ap_tbl = empty_ap_tbl }
597 #ifdef __GLASGOW_HASKELL__
599 stable_ref <- newStablePtr ret
600 let ref = castStablePtrToPtr stable_ref
601 ref2 <- getOrSetTypeableStore ref
603 then deRefStablePtr stable_ref
605 freeStablePtr stable_ref
607 (castPtrToStablePtr ref2)
612 newKey :: IORef Key -> IO Key
613 #ifdef __GLASGOW_HASKELL__
614 newKey _ = do i <- genSym; return (Key i)
616 newKey kloc = do { k@(Key i) <- readIORef kloc ;
617 writeIORef kloc (Key (i+1)) ;
621 #ifdef __GLASGOW_HASKELL__
622 foreign import ccall unsafe "genSymZh"
626 mkTyConKey :: String -> Key
628 = unsafePerformIO $ do
629 let Cache {next_key = kloc, tc_tbl = tbl} = cache
630 mb_k <- HT.lookup tbl str
633 Nothing -> do { k <- newKey kloc ;
634 HT.insert tbl str k ;
637 appKey :: Key -> Key -> Key
639 = unsafePerformIO $ do
640 let Cache {next_key = kloc, ap_tbl = tbl} = cache
641 mb_k <- HT.lookup tbl kpr
644 Nothing -> do { k <- newKey kloc ;
645 HT.insert tbl kpr k ;
650 appKeys :: Key -> [Key] -> Key
651 appKeys k ks = foldl appKey k ks