1 {-# OPTIONS_GHC -fno-implicit-prelude -fallow-overlapping-instances -funbox-strict-fields #-}
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 -----------------------------------------------------------------------------
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
89 import Data.List( foldl, intersperse )
92 #ifdef __GLASGOW_HASKELL__
98 import GHC.Real ( rem, Ratio )
99 import GHC.IOBase (IORef,newIORef,unsafePerformIO)
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
104 import GHC.IOBase ( IO, MVar, Exception, ArithException, IOException,
105 ArrayException, AsyncException, Handle )
107 import GHC.STRef ( STRef )
108 import GHC.Ptr ( Ptr, FunPtr )
109 import GHC.ForeignPtr ( ForeignPtr )
110 import GHC.Stable ( StablePtr, newStablePtr, freeStablePtr,
111 deRefStablePtr, castStablePtrToPtr,
113 import GHC.Exception ( block )
114 import GHC.Arr ( Array, STArray )
119 import Hugs.Prelude ( Key(..), TypeRep(..), TyCon(..), Ratio,
120 Exception, ArithException, IOException,
121 ArrayException, AsyncException, Handle,
122 Ptr, FunPtr, ForeignPtr, StablePtr )
123 import Hugs.IORef ( IORef, newIORef, readIORef, writeIORef )
124 import Hugs.IOExts ( unsafePerformIO )
125 -- For the Typeable instance
126 import Hugs.Array ( Array )
127 import Hugs.ConcBase ( MVar )
131 import NHC.IOExtras (IORef,newIORef,readIORef,writeIORef,unsafePerformIO)
134 -- For the Typeable instance
135 import NHC.FFI ( Ptr,FunPtr,StablePtr,ForeignPtr )
136 import Array ( Array )
139 #include "Typeable.h"
143 -------------------------------------------------------------
145 -- Type representations
147 -------------------------------------------------------------
149 -- | A concrete representation of a (monomorphic) type. 'TypeRep'
150 -- supports reasonably efficient equality.
151 data TypeRep = TypeRep !Key TyCon [TypeRep]
153 -- Compare keys for equality
154 instance Eq TypeRep where
155 (TypeRep k1 _ _) == (TypeRep k2 _ _) = k1 == k2
157 -- | An abstract representation of a type constructor. 'TyCon' objects can
158 -- be built using 'mkTyCon'.
159 data TyCon = TyCon !Key String
161 instance Eq TyCon where
162 (TyCon t1 _) == (TyCon t2 _) = t1 == t2
165 -- | Returns a unique integer associated with a 'TypeRep'. This can
166 -- be used for making a mapping with TypeReps
167 -- as the keys, for example. It is guaranteed that @t1 == t2@ if and only if
168 -- @typeRepKey t1 == typeRepKey t2@.
170 -- It is in the 'IO' monad because the actual value of the key may
171 -- vary from run to run of the program. You should only rely on
172 -- the equality property, not any actual key value. The relative ordering
173 -- of keys has no meaning either.
175 typeRepKey :: TypeRep -> IO Int
176 typeRepKey (TypeRep (Key i) _ _) = return i
179 -- let fTy = mkTyCon "Foo" in show (mkTyConApp (mkTyCon ",,")
182 -- returns "(Foo,Foo,Foo)"
184 -- The TypeRep Show instance promises to print tuple types
185 -- correctly. Tuple type constructors are specified by a
186 -- sequence of commas, e.g., (mkTyCon ",,,,") returns
187 -- the 5-tuple tycon.
189 ----------------- Construction --------------------
191 -- | Applies a type constructor to a sequence of types
192 mkTyConApp :: TyCon -> [TypeRep] -> TypeRep
193 mkTyConApp tc@(TyCon tc_k _) args
194 = TypeRep (appKeys tc_k arg_ks) tc args
196 arg_ks = [k | TypeRep k _ _ <- args]
198 -- | A special case of 'mkTyConApp', which applies the function
199 -- type constructor to a pair of types.
200 mkFunTy :: TypeRep -> TypeRep -> TypeRep
201 mkFunTy f a = mkTyConApp funTc [f,a]
203 -- | Splits a type constructor application
204 splitTyConApp :: TypeRep -> (TyCon,[TypeRep])
205 splitTyConApp (TypeRep _ tc trs) = (tc,trs)
207 -- | Applies a type to a function type. Returns: @'Just' u@ if the
208 -- first argument represents a function of type @t -> u@ and the
209 -- second argument represents a function of type @t@. Otherwise,
210 -- returns 'Nothing'.
211 funResultTy :: TypeRep -> TypeRep -> Maybe TypeRep
212 funResultTy trFun trArg
213 = case splitTyConApp trFun of
214 (tc, [t1,t2]) | tc == funTc && t1 == trArg -> Just t2
217 -- | Adds a TypeRep argument to a TypeRep.
218 mkAppTy :: TypeRep -> TypeRep -> TypeRep
219 mkAppTy (TypeRep tr_k tc trs) arg_tr
220 = let (TypeRep arg_k _ _) = arg_tr
221 in TypeRep (appKey tr_k arg_k) tc (trs++[arg_tr])
223 -- If we enforce the restriction that there is only one
224 -- @TyCon@ for a type & it is shared among all its uses,
225 -- we can map them onto Ints very simply. The benefit is,
226 -- of course, that @TyCon@s can then be compared efficiently.
228 -- Provided the implementor of other @Typeable@ instances
229 -- takes care of making all the @TyCon@s CAFs (toplevel constants),
232 -- If this constraint does turn out to be a sore thumb, changing
233 -- the Eq instance for TyCons is trivial.
235 -- | Builds a 'TyCon' object representing a type constructor. An
236 -- implementation of "Data.Typeable" should ensure that the following holds:
238 -- > mkTyCon "a" == mkTyCon "a"
241 mkTyCon :: String -- ^ the name of the type constructor (should be unique
242 -- in the program, so it might be wise to use the
243 -- fully qualified name).
244 -> TyCon -- ^ A unique 'TyCon' object
245 mkTyCon str = TyCon (mkTyConKey str) str
247 ----------------- Observation ---------------------
249 -- | Observe the type constructor of a type representation
250 typeRepTyCon :: TypeRep -> TyCon
251 typeRepTyCon (TypeRep _ tc _) = tc
253 -- | Observe the argument types of a type representation
254 typeRepArgs :: TypeRep -> [TypeRep]
255 typeRepArgs (TypeRep _ _ args) = args
257 -- | Observe string encoding of a type representation
258 tyConString :: TyCon -> String
259 tyConString (TyCon _ str) = str
261 ----------------- Showing TypeReps --------------------
263 instance Show TypeRep where
264 showsPrec p (TypeRep _ tycon tys) =
266 [] -> showsPrec p tycon
267 [x] | tycon == listTc -> showChar '[' . shows x . showChar ']'
268 [a,r] | tycon == funTc -> showParen (p > 8) $
272 xs | isTupleTyCon tycon -> showTuple xs
279 showsTypeRep :: TypeRep -> ShowS
282 instance Show TyCon where
283 showsPrec _ (TyCon _ s) = showString s
285 isTupleTyCon :: TyCon -> Bool
286 isTupleTyCon (TyCon _ ('(':',':_)) = True
287 isTupleTyCon _ = False
289 -- Some (Show.TypeRep) helpers:
291 showArgs :: Show a => [a] -> ShowS
293 showArgs [a] = showsPrec 10 a
294 showArgs (a:as) = showsPrec 10 a . showString " " . showArgs as
296 showTuple :: [TypeRep] -> ShowS
297 showTuple args = showChar '('
298 . (foldr (.) id $ intersperse (showChar ',')
299 $ map (showsPrec 10) args)
302 -------------------------------------------------------------
304 -- The Typeable class and friends
306 -------------------------------------------------------------
308 -- | The class 'Typeable' allows a concrete representation of a type to
310 class Typeable a where
311 typeOf :: a -> TypeRep
312 -- ^ Takes a value of type @a@ and returns a concrete representation
313 -- of that type. The /value/ of the argument should be ignored by
314 -- any instance of 'Typeable', so that it is safe to pass 'undefined' as
317 -- | Variant for unary type constructors
318 class Typeable1 t where
319 typeOf1 :: t a -> TypeRep
321 -- | For defining a 'Typeable' instance from any 'Typeable1' instance.
322 typeOfDefault :: (Typeable1 t, Typeable a) => t a -> TypeRep
323 typeOfDefault x = typeOf1 x `mkAppTy` typeOf (argType x)
328 -- | Variant for binary type constructors
329 class Typeable2 t where
330 typeOf2 :: t a b -> TypeRep
332 -- | For defining a 'Typeable1' instance from any 'Typeable2' instance.
333 typeOf1Default :: (Typeable2 t, Typeable a) => t a b -> TypeRep
334 typeOf1Default x = typeOf2 x `mkAppTy` typeOf (argType x)
336 argType :: t a b -> a
339 -- | Variant for 3-ary type constructors
340 class Typeable3 t where
341 typeOf3 :: t a b c -> TypeRep
343 -- | For defining a 'Typeable2' instance from any 'Typeable3' instance.
344 typeOf2Default :: (Typeable3 t, Typeable a) => t a b c -> TypeRep
345 typeOf2Default x = typeOf3 x `mkAppTy` typeOf (argType x)
347 argType :: t a b c -> a
350 -- | Variant for 4-ary type constructors
351 class Typeable4 t where
352 typeOf4 :: t a b c d -> TypeRep
354 -- | For defining a 'Typeable3' instance from any 'Typeable4' instance.
355 typeOf3Default :: (Typeable4 t, Typeable a) => t a b c d -> TypeRep
356 typeOf3Default x = typeOf4 x `mkAppTy` typeOf (argType x)
358 argType :: t a b c d -> a
361 -- | Variant for 5-ary type constructors
362 class Typeable5 t where
363 typeOf5 :: t a b c d e -> TypeRep
365 -- | For defining a 'Typeable4' instance from any 'Typeable5' instance.
366 typeOf4Default :: (Typeable5 t, Typeable a) => t a b c d e -> TypeRep
367 typeOf4Default x = typeOf5 x `mkAppTy` typeOf (argType x)
369 argType :: t a b c d e -> a
372 -- | Variant for 6-ary type constructors
373 class Typeable6 t where
374 typeOf6 :: t a b c d e f -> TypeRep
376 -- | For defining a 'Typeable5' instance from any 'Typeable6' instance.
377 typeOf5Default :: (Typeable6 t, Typeable a) => t a b c d e f -> TypeRep
378 typeOf5Default x = typeOf6 x `mkAppTy` typeOf (argType x)
380 argType :: t a b c d e f -> a
383 -- | Variant for 7-ary type constructors
384 class Typeable7 t where
385 typeOf7 :: t a b c d e f g -> TypeRep
387 -- | For defining a 'Typeable6' instance from any 'Typeable7' instance.
388 typeOf6Default :: (Typeable7 t, Typeable a) => t a b c d e f g -> TypeRep
389 typeOf6Default x = typeOf7 x `mkAppTy` typeOf (argType x)
391 argType :: t a b c d e f g -> a
394 #ifdef __GLASGOW_HASKELL__
395 -- Given a @Typeable@/n/ instance for an /n/-ary type constructor,
396 -- define the instances for partial applications.
397 -- Programmers using non-GHC implementations must do this manually
398 -- for each type constructor.
399 -- (The INSTANCE_TYPEABLE/n/ macros in Typeable.h include this.)
401 -- | One Typeable instance for all Typeable1 instances
402 instance (Typeable1 s, Typeable a)
403 => Typeable (s a) where
404 typeOf = typeOfDefault
406 -- | One Typeable1 instance for all Typeable2 instances
407 instance (Typeable2 s, Typeable a)
408 => Typeable1 (s a) where
409 typeOf1 = typeOf1Default
411 -- | One Typeable2 instance for all Typeable3 instances
412 instance (Typeable3 s, Typeable a)
413 => Typeable2 (s a) where
414 typeOf2 = typeOf2Default
416 -- | One Typeable3 instance for all Typeable4 instances
417 instance (Typeable4 s, Typeable a)
418 => Typeable3 (s a) where
419 typeOf3 = typeOf3Default
421 -- | One Typeable4 instance for all Typeable5 instances
422 instance (Typeable5 s, Typeable a)
423 => Typeable4 (s a) where
424 typeOf4 = typeOf4Default
426 -- | One Typeable5 instance for all Typeable6 instances
427 instance (Typeable6 s, Typeable a)
428 => Typeable5 (s a) where
429 typeOf5 = typeOf5Default
431 -- | One Typeable6 instance for all Typeable7 instances
432 instance (Typeable7 s, Typeable a)
433 => Typeable6 (s a) where
434 typeOf6 = typeOf6Default
436 #endif /* __GLASGOW_HASKELL__ */
438 -------------------------------------------------------------
442 -------------------------------------------------------------
444 -- | The type-safe cast operation
445 cast :: (Typeable a, Typeable b) => a -> Maybe b
448 r = if typeOf x == typeOf (fromJust r)
449 then Just $ unsafeCoerce x
452 -- | A flexible variation parameterised in a type constructor
453 gcast :: (Typeable a, Typeable b) => c a -> Maybe (c b)
456 r = if typeOf (getArg x) == typeOf (getArg (fromJust r))
457 then Just $ unsafeCoerce x
463 gcast1 :: (Typeable1 t, Typeable1 t') => c (t a) -> Maybe (c (t' a))
466 r = if typeOf1 (getArg x) == typeOf1 (getArg (fromJust r))
467 then Just $ unsafeCoerce x
472 -- | Cast for * -> * -> *
473 gcast2 :: (Typeable2 t, Typeable2 t') => c (t a b) -> Maybe (c (t' a b))
476 r = if typeOf2 (getArg x) == typeOf2 (getArg (fromJust r))
477 then Just $ unsafeCoerce x
482 -------------------------------------------------------------
484 -- Instances of the Typeable classes for Prelude types
486 -------------------------------------------------------------
488 INSTANCE_TYPEABLE0((),unitTc,"()")
489 INSTANCE_TYPEABLE1([],listTc,"[]")
490 INSTANCE_TYPEABLE1(Maybe,maybeTc,"Maybe")
491 INSTANCE_TYPEABLE1(Ratio,ratioTc,"Ratio")
492 INSTANCE_TYPEABLE2(Either,eitherTc,"Either")
493 INSTANCE_TYPEABLE2((->),funTc,"->")
494 INSTANCE_TYPEABLE1(IO,ioTc,"IO")
496 #if defined(__GLASGOW_HASKELL__) || defined(__HUGS__)
497 -- Types defined in GHC.IOBase
498 INSTANCE_TYPEABLE1(MVar,mvarTc,"MVar" )
499 INSTANCE_TYPEABLE0(Exception,exceptionTc,"Exception")
500 INSTANCE_TYPEABLE0(IOException,ioExceptionTc,"IOException")
501 INSTANCE_TYPEABLE0(ArithException,arithExceptionTc,"ArithException")
502 INSTANCE_TYPEABLE0(ArrayException,arrayExceptionTc,"ArrayException")
503 INSTANCE_TYPEABLE0(AsyncException,asyncExceptionTc,"AsyncException")
506 -- Types defined in GHC.Arr
507 INSTANCE_TYPEABLE2(Array,arrayTc,"Array")
509 #ifdef __GLASGOW_HASKELL__
510 -- Hugs has these too, but their Typeable<n> instances are defined
511 -- elsewhere to keep this module within Haskell 98.
512 -- This is important because every invocation of runhugs or ffihugs
513 -- uses this module via Data.Dynamic.
514 INSTANCE_TYPEABLE2(ST,stTc,"ST")
515 INSTANCE_TYPEABLE2(STRef,stRefTc,"STRef")
516 INSTANCE_TYPEABLE3(STArray,sTArrayTc,"STArray")
520 INSTANCE_TYPEABLE2((,),pairTc,"(,)")
521 INSTANCE_TYPEABLE3((,,),tup3Tc,"(,,)")
524 tup4Tc = mkTyCon "(,,,)"
526 instance Typeable4 (,,,) where
527 typeOf4 tu = mkTyConApp tup4Tc []
530 tup5Tc = mkTyCon "(,,,,)"
532 instance Typeable5 (,,,,) where
533 typeOf5 tu = mkTyConApp tup5Tc []
536 tup6Tc = mkTyCon "(,,,,,)"
538 instance Typeable6 (,,,,,) where
539 typeOf6 tu = mkTyConApp tup6Tc []
542 tup7Tc = mkTyCon "(,,,,,,)"
544 instance Typeable7 (,,,,,,) where
545 typeOf7 tu = mkTyConApp tup7Tc []
548 INSTANCE_TYPEABLE1(Ptr,ptrTc,"Ptr")
549 INSTANCE_TYPEABLE1(FunPtr,funPtrTc,"FunPtr")
550 INSTANCE_TYPEABLE1(ForeignPtr,foreignPtrTc,"ForeignPtr")
551 INSTANCE_TYPEABLE1(StablePtr,stablePtrTc,"StablePtr")
552 INSTANCE_TYPEABLE1(IORef,iORefTc,"IORef")
554 -------------------------------------------------------
556 -- Generate Typeable instances for standard datatypes
558 -------------------------------------------------------
560 INSTANCE_TYPEABLE0(Bool,boolTc,"Bool")
561 INSTANCE_TYPEABLE0(Char,charTc,"Char")
562 INSTANCE_TYPEABLE0(Float,floatTc,"Float")
563 INSTANCE_TYPEABLE0(Double,doubleTc,"Double")
564 INSTANCE_TYPEABLE0(Int,intTc,"Int")
566 INSTANCE_TYPEABLE0(Word,wordTc,"Word" )
568 INSTANCE_TYPEABLE0(Integer,integerTc,"Integer")
569 INSTANCE_TYPEABLE0(Ordering,orderingTc,"Ordering")
570 INSTANCE_TYPEABLE0(Handle,handleTc,"Handle")
572 INSTANCE_TYPEABLE0(Int8,int8Tc,"Int8")
573 INSTANCE_TYPEABLE0(Int16,int16Tc,"Int16")
574 INSTANCE_TYPEABLE0(Int32,int32Tc,"Int32")
575 INSTANCE_TYPEABLE0(Int64,int64Tc,"Int64")
577 INSTANCE_TYPEABLE0(Word8,word8Tc,"Word8" )
578 INSTANCE_TYPEABLE0(Word16,word16Tc,"Word16")
579 INSTANCE_TYPEABLE0(Word32,word32Tc,"Word32")
580 INSTANCE_TYPEABLE0(Word64,word64Tc,"Word64")
582 INSTANCE_TYPEABLE0(TyCon,tyconTc,"TyCon")
583 INSTANCE_TYPEABLE0(TypeRep,typeRepTc,"TypeRep")
585 #ifdef __GLASGOW_HASKELL__
586 INSTANCE_TYPEABLE0(RealWorld,realWorldTc,"RealWorld")
589 ---------------------------------------------
593 ---------------------------------------------
596 newtype Key = Key Int deriving( Eq )
599 data KeyPr = KeyPr !Key !Key deriving( Eq )
601 hashKP :: KeyPr -> Int32
602 hashKP (KeyPr (Key k1) (Key k2)) = (HT.hashInt k1 + HT.hashInt k2) `rem` HT.prime
604 data Cache = Cache { next_key :: !(IORef Key), -- Not used by GHC (calls genSym instead)
605 tc_tbl :: !(HT.HashTable String Key),
606 ap_tbl :: !(HT.HashTable KeyPr Key) }
608 {-# NOINLINE cache #-}
609 #ifdef __GLASGOW_HASKELL__
610 foreign import ccall unsafe "RtsTypeable.h getOrSetTypeableStore"
611 getOrSetTypeableStore :: Ptr a -> IO (Ptr a)
615 cache = unsafePerformIO $ do
616 empty_tc_tbl <- HT.new (==) HT.hashString
617 empty_ap_tbl <- HT.new (==) hashKP
618 key_loc <- newIORef (Key 1)
619 let ret = Cache { next_key = key_loc,
620 tc_tbl = empty_tc_tbl,
621 ap_tbl = empty_ap_tbl }
622 #ifdef __GLASGOW_HASKELL__
624 stable_ref <- newStablePtr ret
625 let ref = castStablePtrToPtr stable_ref
626 ref2 <- getOrSetTypeableStore ref
628 then deRefStablePtr stable_ref
630 freeStablePtr stable_ref
632 (castPtrToStablePtr ref2)
637 newKey :: IORef Key -> IO Key
638 #ifdef __GLASGOW_HASKELL__
639 newKey kloc = do i <- genSym; return (Key i)
641 newKey kloc = do { k@(Key i) <- readIORef kloc ;
642 writeIORef kloc (Key (i+1)) ;
646 #ifdef __GLASGOW_HASKELL__
647 foreign import ccall unsafe "genSymZh"
651 mkTyConKey :: String -> Key
653 = unsafePerformIO $ do
654 let Cache {next_key = kloc, tc_tbl = tbl} = cache
655 mb_k <- HT.lookup tbl str
658 Nothing -> do { k <- newKey kloc ;
659 HT.insert tbl str k ;
662 appKey :: Key -> Key -> Key
664 = unsafePerformIO $ do
665 let Cache {next_key = kloc, ap_tbl = tbl} = cache
666 mb_k <- HT.lookup tbl kpr
669 Nothing -> do { k <- newKey kloc ;
670 HT.insert tbl kpr k ;
675 appKeys :: Key -> [Key] -> Key
676 appKeys k ks = foldl appKey k ks