1 {-# OPTIONS_GHC -fno-implicit-prelude -fallow-overlapping-instances #-}
3 -- The -fallow-overlapping-instances 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.Generics" uses Typeable
25 -- and type-safe cast (but not dynamics) to support the \"Scrap your
26 -- boilerplate\" style of generic programming.
28 -- Note, only relevant if you use dynamic linking. If you have a program
29 -- that is statically linked with Data.Typeable, and then dynamically link
30 -- a program that also uses Data.Typeable, you'll get two copies of the module.
31 -- That's fine, but behind the scenes, the module uses a mutable variable to
32 -- allocate unique Ids to type constructors. So in the situation described,
33 -- there'll be two separate Id allocators, which aren't comparable to each other.
34 -- This can lead to chaos. (It's a bug that we will fix.) None of
35 -- this matters if you aren't using dynamic linking.
37 -----------------------------------------------------------------------------
42 -- * The Typeable class
43 Typeable( typeOf ), -- :: a -> TypeRep
46 cast, -- :: (Typeable a, Typeable b) => a -> Maybe b
47 gcast, -- a generalisation of cast
49 -- * Type representations
50 TypeRep, -- abstract, instance of: Eq, Show, Typeable
51 TyCon, -- abstract, instance of: Eq, Show, Typeable
53 -- * Construction of type representations
54 mkTyCon, -- :: String -> TyCon
55 mkTyConApp, -- :: TyCon -> [TypeRep] -> TypeRep
56 mkAppTy, -- :: TypeRep -> TypeRep -> TypeRep
57 mkFunTy, -- :: TypeRep -> TypeRep -> TypeRep
59 -- * Observation of type representations
60 splitTyConApp, -- :: TypeRep -> (TyCon, [TypeRep])
61 funResultTy, -- :: TypeRep -> TypeRep -> Maybe TypeRep
62 typeRepTyCon, -- :: TypeRep -> TyCon
63 typeRepArgs, -- :: TypeRep -> [TypeRep]
64 tyConString, -- :: TyCon -> String
66 -- * The other Typeable classes
67 -- | /Note:/ The general instances are provided for GHC only.
68 Typeable1( typeOf1 ), -- :: t a -> TypeRep
69 Typeable2( typeOf2 ), -- :: t a b -> TypeRep
70 Typeable3( typeOf3 ), -- :: t a b c -> TypeRep
71 Typeable4( typeOf4 ), -- :: t a b c d -> TypeRep
72 Typeable5( typeOf5 ), -- :: t a b c d e -> TypeRep
73 Typeable6( typeOf6 ), -- :: t a b c d e f -> TypeRep
74 Typeable7( typeOf7 ), -- :: t a b c d e f g -> TypeRep
75 gcast1, -- :: ... => c (t a) -> Maybe (c (t' a))
76 gcast2, -- :: ... => c (t a b) -> Maybe (c (t' a b))
78 -- * Default instances
79 -- | /Note:/ These are not needed by GHC, for which these instances
80 -- are generated by general instance declarations.
81 typeOfDefault, -- :: (Typeable1 t, Typeable a) => t a -> TypeRep
82 typeOf1Default, -- :: (Typeable2 t, Typeable a) => t a b -> TypeRep
83 typeOf2Default, -- :: (Typeable3 t, Typeable a) => t a b c -> TypeRep
84 typeOf3Default, -- :: (Typeable4 t, Typeable a) => t a b c d -> TypeRep
85 typeOf4Default, -- :: (Typeable5 t, Typeable a) => t a b c d e -> TypeRep
86 typeOf5Default, -- :: (Typeable6 t, Typeable a) => t a b c d e f -> TypeRep
87 typeOf6Default -- :: (Typeable7 t, Typeable a) => t a b c d e f g -> TypeRep
91 import qualified Data.HashTable as HT
96 import Data.List( foldl )
98 #ifdef __GLASGOW_HASKELL__
104 import GHC.Real ( rem, Ratio )
105 import GHC.IOBase (IORef,newIORef,unsafePerformIO)
107 -- These imports are so we can define Typeable instances
108 -- It'd be better to give Typeable instances in the modules themselves
109 -- but they all have to be compiled before Typeable
110 import GHC.IOBase ( IO, MVar, Exception, ArithException, IOException,
111 ArrayException, AsyncException, Handle )
113 import GHC.STRef ( STRef )
114 import GHC.Ptr ( Ptr, FunPtr )
115 import GHC.ForeignPtr ( ForeignPtr )
116 import GHC.Stable ( StablePtr )
117 import GHC.Arr ( Array, STArray )
122 import Hugs.Prelude ( Key(..), TypeRep(..), TyCon(..), Ratio,
123 Exception, ArithException, IOException,
124 ArrayException, AsyncException, Handle,
125 Ptr, FunPtr, ForeignPtr, StablePtr )
126 import Hugs.IORef ( IORef, newIORef, readIORef, writeIORef )
127 import Hugs.IOExts ( unsafePerformIO, unsafeCoerce )
128 -- For the Typeable instance
129 import Hugs.Array ( Array )
130 import Hugs.ConcBase ( MVar )
133 #ifdef __GLASGOW_HASKELL__
134 unsafeCoerce :: a -> b
135 unsafeCoerce = unsafeCoerce#
139 import NonStdUnsafeCoerce (unsafeCoerce)
140 import NHC.IOExtras (IORef,newIORef,readIORef,writeIORef,unsafePerformIO)
143 -- For the Typeable instance
144 import NHC.FFI ( Ptr,FunPtr,StablePtr,ForeignPtr )
145 import Array ( Array )
148 #include "Typeable.h"
152 -------------------------------------------------------------
154 -- Type representations
156 -------------------------------------------------------------
158 -- | A concrete representation of a (monomorphic) type. 'TypeRep'
159 -- supports reasonably efficient equality.
160 data TypeRep = TypeRep !Key TyCon [TypeRep]
162 -- Compare keys for equality
163 instance Eq TypeRep where
164 (TypeRep k1 _ _) == (TypeRep k2 _ _) = k1 == k2
166 -- | An abstract representation of a type constructor. 'TyCon' objects can
167 -- be built using 'mkTyCon'.
168 data TyCon = TyCon !Key String
170 instance Eq TyCon where
171 (TyCon t1 _) == (TyCon t2 _) = t1 == t2
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 tycon xs
276 instance Show TyCon where
277 showsPrec _ (TyCon _ s) = showString s
279 isTupleTyCon :: TyCon -> Bool
280 isTupleTyCon (TyCon _ (',':_)) = True
281 isTupleTyCon _ = False
283 -- Some (Show.TypeRep) helpers:
285 showArgs :: Show a => [a] -> ShowS
287 showArgs [a] = showsPrec 10 a
288 showArgs (a:as) = showsPrec 10 a . showString " " . showArgs as
290 showTuple :: TyCon -> [TypeRep] -> ShowS
291 showTuple (TyCon _ str) args = showChar '(' . go str args
293 go [] [a] = showsPrec 10 a . showChar ')'
294 go _ [] = showChar ')' -- a failure condition, really.
295 go (',':xs) (a:as) = showsPrec 10 a . showChar ',' . go xs as
296 go _ _ = showChar ')'
298 -------------------------------------------------------------
300 -- The Typeable class and friends
302 -------------------------------------------------------------
304 -- | The class 'Typeable' allows a concrete representation of a type to
306 class Typeable a where
307 typeOf :: a -> TypeRep
308 -- ^ Takes a value of type @a@ and returns a concrete representation
309 -- of that type. The /value/ of the argument should be ignored by
310 -- any instance of 'Typeable', so that it is safe to pass 'undefined' as
313 -- | Variant for unary type constructors
314 class Typeable1 t where
315 typeOf1 :: t a -> TypeRep
317 -- | For defining a 'Typeable' instance from any 'Typeable1' instance.
318 typeOfDefault :: (Typeable1 t, Typeable a) => t a -> TypeRep
319 typeOfDefault x = typeOf1 x `mkAppTy` typeOf (argType x)
324 -- | Variant for binary type constructors
325 class Typeable2 t where
326 typeOf2 :: t a b -> TypeRep
328 -- | For defining a 'Typeable1' instance from any 'Typeable2' instance.
329 typeOf1Default :: (Typeable2 t, Typeable a) => t a b -> TypeRep
330 typeOf1Default x = typeOf2 x `mkAppTy` typeOf (argType x)
332 argType :: t a b -> a
335 -- | Variant for 3-ary type constructors
336 class Typeable3 t where
337 typeOf3 :: t a b c -> TypeRep
339 -- | For defining a 'Typeable2' instance from any 'Typeable3' instance.
340 typeOf2Default :: (Typeable3 t, Typeable a) => t a b c -> TypeRep
341 typeOf2Default x = typeOf3 x `mkAppTy` typeOf (argType x)
343 argType :: t a b c -> a
346 -- | Variant for 4-ary type constructors
347 class Typeable4 t where
348 typeOf4 :: t a b c d -> TypeRep
350 -- | For defining a 'Typeable3' instance from any 'Typeable4' instance.
351 typeOf3Default :: (Typeable4 t, Typeable a) => t a b c d -> TypeRep
352 typeOf3Default x = typeOf4 x `mkAppTy` typeOf (argType x)
354 argType :: t a b c d -> a
357 -- | Variant for 5-ary type constructors
358 class Typeable5 t where
359 typeOf5 :: t a b c d e -> TypeRep
361 -- | For defining a 'Typeable4' instance from any 'Typeable5' instance.
362 typeOf4Default :: (Typeable5 t, Typeable a) => t a b c d e -> TypeRep
363 typeOf4Default x = typeOf5 x `mkAppTy` typeOf (argType x)
365 argType :: t a b c d e -> a
368 -- | Variant for 6-ary type constructors
369 class Typeable6 t where
370 typeOf6 :: t a b c d e f -> TypeRep
372 -- | For defining a 'Typeable5' instance from any 'Typeable6' instance.
373 typeOf5Default :: (Typeable6 t, Typeable a) => t a b c d e f -> TypeRep
374 typeOf5Default x = typeOf6 x `mkAppTy` typeOf (argType x)
376 argType :: t a b c d e f -> a
379 -- | Variant for 7-ary type constructors
380 class Typeable7 t where
381 typeOf7 :: t a b c d e f g -> TypeRep
383 -- | For defining a 'Typeable6' instance from any 'Typeable7' instance.
384 typeOf6Default :: (Typeable7 t, Typeable a) => t a b c d e f g -> TypeRep
385 typeOf6Default x = typeOf7 x `mkAppTy` typeOf (argType x)
387 argType :: t a b c d e f g -> a
390 #ifdef __GLASGOW_HASKELL__
391 -- Given a @Typeable@/n/ instance for an /n/-ary type constructor,
392 -- define the instances for partial applications.
393 -- Programmers using non-GHC implementations must do this manually
394 -- for each type constructor.
395 -- (The INSTANCE_TYPEABLE/n/ macros in Typeable.h include this.)
397 -- | One Typeable instance for all Typeable1 instances
398 instance (Typeable1 s, Typeable a)
399 => Typeable (s a) where
400 typeOf = typeOfDefault
402 -- | One Typeable1 instance for all Typeable2 instances
403 instance (Typeable2 s, Typeable a)
404 => Typeable1 (s a) where
405 typeOf1 = typeOf1Default
407 -- | One Typeable2 instance for all Typeable3 instances
408 instance (Typeable3 s, Typeable a)
409 => Typeable2 (s a) where
410 typeOf2 = typeOf2Default
412 -- | One Typeable3 instance for all Typeable4 instances
413 instance (Typeable4 s, Typeable a)
414 => Typeable3 (s a) where
415 typeOf3 = typeOf3Default
417 -- | One Typeable4 instance for all Typeable5 instances
418 instance (Typeable5 s, Typeable a)
419 => Typeable4 (s a) where
420 typeOf4 = typeOf4Default
422 -- | One Typeable5 instance for all Typeable6 instances
423 instance (Typeable6 s, Typeable a)
424 => Typeable5 (s a) where
425 typeOf5 = typeOf5Default
427 -- | One Typeable6 instance for all Typeable7 instances
428 instance (Typeable7 s, Typeable a)
429 => Typeable6 (s a) where
430 typeOf6 = typeOf6Default
432 #endif /* __GLASGOW_HASKELL__ */
434 -------------------------------------------------------------
438 -------------------------------------------------------------
440 -- | The type-safe cast operation
441 cast :: (Typeable a, Typeable b) => a -> Maybe b
444 r = if typeOf x == typeOf (fromJust r)
445 then Just $ unsafeCoerce x
448 -- | A flexible variation parameterised in a type constructor
449 gcast :: (Typeable a, Typeable b) => c a -> Maybe (c b)
452 r = if typeOf (getArg x) == typeOf (getArg (fromJust r))
453 then Just $ unsafeCoerce x
459 gcast1 :: (Typeable1 t, Typeable1 t') => c (t a) -> Maybe (c (t' a))
462 r = if typeOf1 (getArg x) == typeOf1 (getArg (fromJust r))
463 then Just $ unsafeCoerce x
468 -- | Cast for * -> * -> *
469 gcast2 :: (Typeable2 t, Typeable2 t') => c (t a b) -> Maybe (c (t' a b))
472 r = if typeOf2 (getArg x) == typeOf2 (getArg (fromJust r))
473 then Just $ unsafeCoerce x
478 -------------------------------------------------------------
480 -- Instances of the Typeable classes for Prelude types
482 -------------------------------------------------------------
484 INSTANCE_TYPEABLE0((),unitTc,"()")
485 INSTANCE_TYPEABLE1([],listTc,"[]")
486 INSTANCE_TYPEABLE1(Maybe,maybeTc,"Maybe")
487 INSTANCE_TYPEABLE1(Ratio,ratioTc,"Ratio")
488 INSTANCE_TYPEABLE2(Either,eitherTc,"Either")
489 INSTANCE_TYPEABLE2((->),funTc,"->")
490 INSTANCE_TYPEABLE1(IO,ioTc,"IO")
492 #if defined(__GLASGOW_HASKELL__) || defined(__HUGS__)
493 -- Types defined in GHC.IOBase
494 INSTANCE_TYPEABLE1(MVar,mvarTc,"MVar" )
495 INSTANCE_TYPEABLE0(Exception,exceptionTc,"Exception")
496 INSTANCE_TYPEABLE0(IOException,ioExceptionTc,"IOException")
497 INSTANCE_TYPEABLE0(ArithException,arithExceptionTc,"ArithException")
498 INSTANCE_TYPEABLE0(ArrayException,arrayExceptionTc,"ArrayException")
499 INSTANCE_TYPEABLE0(AsyncException,asyncExceptionTc,"AsyncException")
502 -- Types defined in GHC.Arr
503 INSTANCE_TYPEABLE2(Array,arrayTc,"Array")
505 #ifdef __GLASGOW_HASKELL__
506 -- Hugs has these too, but their Typeable<n> instances are defined
507 -- elsewhere to keep this module within Haskell 98.
508 -- This is important because every invocation of runhugs or ffihugs
509 -- uses this module via Data.Dynamic.
510 INSTANCE_TYPEABLE2(ST,stTc,"ST")
511 INSTANCE_TYPEABLE2(STRef,stRefTc,"STRef")
512 INSTANCE_TYPEABLE3(STArray,sTArrayTc,"STArray")
516 INSTANCE_TYPEABLE2((,),pairTc,",")
517 INSTANCE_TYPEABLE3((,,),tup3Tc,",,")
520 tup4Tc = mkTyCon ",,,"
522 instance Typeable4 (,,,) where
523 typeOf4 tu = mkTyConApp tup4Tc []
526 tup5Tc = mkTyCon ",,,,"
528 instance Typeable5 (,,,,) where
529 typeOf5 tu = mkTyConApp tup5Tc []
532 tup6Tc = mkTyCon ",,,,,"
534 instance Typeable6 (,,,,,) where
535 typeOf6 tu = mkTyConApp tup6Tc []
538 tup7Tc = mkTyCon ",,,,,,"
540 instance Typeable7 (,,,,,,) where
541 typeOf7 tu = mkTyConApp tup7Tc []
544 INSTANCE_TYPEABLE1(Ptr,ptrTc,"Ptr")
545 INSTANCE_TYPEABLE1(FunPtr,funPtrTc,"FunPtr")
546 INSTANCE_TYPEABLE1(ForeignPtr,foreignPtrTc,"ForeignPtr")
547 INSTANCE_TYPEABLE1(StablePtr,stablePtrTc,"StablePtr")
548 INSTANCE_TYPEABLE1(IORef,iORefTc,"IORef")
550 -------------------------------------------------------
552 -- Generate Typeable instances for standard datatypes
554 -------------------------------------------------------
556 INSTANCE_TYPEABLE0(Bool,boolTc,"Bool")
557 INSTANCE_TYPEABLE0(Char,charTc,"Char")
558 INSTANCE_TYPEABLE0(Float,floatTc,"Float")
559 INSTANCE_TYPEABLE0(Double,doubleTc,"Double")
560 INSTANCE_TYPEABLE0(Int,intTc,"Int")
562 INSTANCE_TYPEABLE0(Word,wordTc,"Word" )
564 INSTANCE_TYPEABLE0(Integer,integerTc,"Integer")
565 INSTANCE_TYPEABLE0(Ordering,orderingTc,"Ordering")
566 INSTANCE_TYPEABLE0(Handle,handleTc,"Handle")
568 INSTANCE_TYPEABLE0(Int8,int8Tc,"Int8")
569 INSTANCE_TYPEABLE0(Int16,int16Tc,"Int16")
570 INSTANCE_TYPEABLE0(Int32,int32Tc,"Int32")
571 INSTANCE_TYPEABLE0(Int64,int64Tc,"Int64")
573 INSTANCE_TYPEABLE0(Word8,word8Tc,"Word8" )
574 INSTANCE_TYPEABLE0(Word16,word16Tc,"Word16")
575 INSTANCE_TYPEABLE0(Word32,word32Tc,"Word32")
576 INSTANCE_TYPEABLE0(Word64,word64Tc,"Word64")
578 INSTANCE_TYPEABLE0(TyCon,tyconTc,"TyCon")
579 INSTANCE_TYPEABLE0(TypeRep,typeRepTc,"TypeRep")
581 #ifdef __GLASGOW_HASKELL__
582 INSTANCE_TYPEABLE0(RealWorld,realWorldTc,"RealWorld")
585 ---------------------------------------------
589 ---------------------------------------------
592 newtype Key = Key Int deriving( Eq )
595 data KeyPr = KeyPr !Key !Key deriving( Eq )
597 hashKP :: KeyPr -> Int32
598 hashKP (KeyPr (Key k1) (Key k2)) = (HT.hashInt k1 + HT.hashInt k2) `rem` HT.prime
600 data Cache = Cache { next_key :: !(IORef Key), -- Not used by GHC (calls genSym instead)
601 tc_tbl :: !(HT.HashTable String Key),
602 ap_tbl :: !(HT.HashTable KeyPr Key) }
604 {-# NOINLINE cache #-}
606 cache = unsafePerformIO $ do
607 empty_tc_tbl <- HT.new (==) HT.hashString
608 empty_ap_tbl <- HT.new (==) hashKP
609 key_loc <- newIORef (Key 1)
610 return (Cache { next_key = key_loc,
611 tc_tbl = empty_tc_tbl,
612 ap_tbl = empty_ap_tbl })
614 newKey :: IORef Key -> IO Key
615 #ifdef __GLASGOW_HASKELL__
616 newKey kloc = do i <- genSym; return (Key i)
618 newKey kloc = do { k@(Key i) <- readIORef kloc ;
619 writeIORef kloc (Key (i+1)) ;
623 #ifdef __GLASGOW_HASKELL__
624 -- In GHC we use the RTS's genSym function to get a new unique,
625 -- because in GHCi we might have two copies of the Data.Typeable
626 -- library running (one in the compiler and one in the running
627 -- program), and we need to make sure they don't share any keys.
629 -- This is really a hack. A better solution would be to centralise the
630 -- whole mutable state used by this module, i.e. both hashtables. But
631 -- the current solution solves the immediate problem, which is that
632 -- dynamics generated in one world with one type were erroneously
633 -- being recognised by the other world as having a different type.
634 foreign import ccall unsafe "genSymZh"
638 mkTyConKey :: String -> Key
640 = unsafePerformIO $ do
641 let Cache {next_key = kloc, tc_tbl = tbl} = cache
642 mb_k <- HT.lookup tbl str
645 Nothing -> do { k <- newKey kloc ;
646 HT.insert tbl str k ;
649 appKey :: Key -> Key -> Key
651 = unsafePerformIO $ do
652 let Cache {next_key = kloc, ap_tbl = tbl} = cache
653 mb_k <- HT.lookup tbl kpr
656 Nothing -> do { k <- newKey kloc ;
657 HT.insert tbl kpr k ;
662 appKeys :: Key -> [Key] -> Key
663 appKeys k ks = foldl appKey k ks