-----------------------------------------------------------------------------
-- |
-- Module : Data.Typeable
--- Copyright : (c) The University of Glasgow 2001
+-- Copyright : (c) The University of Glasgow, CWI 2001--2004
-- License : BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer : libraries@haskell.org
-- * Type-safe cast
cast, -- :: (Typeable a, Typeable b) => a -> Maybe b
- castss, -- a cast for kind "* -> *"
- castarr, -- another convenient variation
+ gcast, -- a generalisation of cast
-- * Type representations
TypeRep, -- abstract, instance of: Eq, Show, Typeable
mkAppTy, -- :: TyCon -> [TypeRep] -> TypeRep
mkFunTy, -- :: TypeRep -> TypeRep -> TypeRep
applyTy, -- :: TypeRep -> TypeRep -> Maybe TypeRep
+ popStarTy, -- :: TypeRep -> TypeRep -> TypeRep
-- * Observation of type representations
typerepTyCon, -- :: TypeRep -> TyCon
typerepArgs, -- :: TypeRep -> [TypeRep]
- tyconString -- :: TyCon -> String
-
+ tyconString, -- :: TyCon -> String
+
+ -- * The other Typeable classes
+ Typeable1( typeOf1 ), -- :: t a -> TypeRep
+ Typeable2( typeOf2 ), -- :: t a b -> TypeRep
+ Typeable3( typeOf3 ), -- :: t a b c -> TypeRep
+ Typeable4( typeOf4 ), -- :: t a b c d -> TypeRep
+ Typeable5( typeOf5 ), -- :: t a b c d e -> TypeRep
+ Typeable6( typeOf6 ), -- :: t a b c d e f -> TypeRep
+ Typeable7( typeOf7 ), -- :: t a b c d e f g -> TypeRep
+ gcast1, -- :: ... => c (t a) -> Maybe (c (t' a))
+ gcast2 -- :: ... => c (t a b) -> Maybe (c (t' a b))
) where
import GHC.Float
import GHC.Real( rem, Ratio )
import GHC.IOBase
-import GHC.Ptr -- So we can give Typeable instance for Ptr
-import GHC.Stable -- So we can give Typeable instance for StablePtr
+import GHC.Ptr -- So we can give Typeable instance for Ptr
+import GHC.Stable -- So we can give Typeable instance for StablePtr
#endif
#ifdef __HUGS__
#ifndef __HUGS__
+
-------------------------------------------------------------
--
-- Type representations
-- sequence of commas, e.g., (mkTyCon ",,,,") returns
-- the 5-tuple tycon.
+
----------------- Construction --------------------
-- | Applies a type constructor to a sequence of types
where
arg_ks = [k | TypeRep k _ _ <- args]
+
+-- The function type constructor
funTc :: TyCon
funTc = mkTyCon "->"
+
-- | A special case of 'mkAppTy', which applies the function
-- type constructor to a pair of types.
mkFunTy :: TypeRep -> TypeRep -> TypeRep
mkFunTy f a = mkAppTy funTc [f,a]
+
-- | Applies a type to a function type. Returns: @'Just' u@ if the
-- first argument represents a function of type @t -> u@ and the
-- second argument represents a function of type @t@. Otherwise,
| tc == funTc && t1 == t3 = Just t2
applyTy _ _ = Nothing
+
+-- | Adds a TypeRep argument to a TypeRep.
+popStarTy :: TypeRep -> TypeRep -> TypeRep
+popStarTy (TypeRep tr_k tc trs) arg_tr
+ = let (TypeRep arg_k _ _) = arg_tr
+ in TypeRep (appKey tr_k arg_k) tc (trs++[arg_tr])
+
+
-- If we enforce the restriction that there is only one
-- @TyCon@ for a type & it is shared among all its uses,
-- we can map them onto Ints very simply. The benefit is,
[] -> showsPrec p tycon
[x] | tycon == listTc -> showChar '[' . shows x . showChar ']'
[a,r] | tycon == funTc -> showParen (p > 8) $
- showsPrec 9 a . showString " -> " . showsPrec 8 r
+ showsPrec 9 a .
+ showString " -> " .
+ showsPrec 8 r
xs | isTupleTyCon tycon -> showTuple tycon xs
| otherwise ->
showParen (p > 9) $
isTupleTyCon (TyCon _ (',':_)) = True
isTupleTyCon _ = False
+
-- Some (Show.TypeRep) helpers:
showArgs :: Show a => [a] -> ShowS
-------------------------------------------------------------
--
--- The Typeable class
+-- The Typeable class and friends
--
-------------------------------------------------------------
+
-- | The class 'Typeable' allows a concrete representation of a type to
-- be calculated.
class Typeable a where
-- any instance of 'Typeable', so that it is safe to pass 'undefined' as
-- the argument.
+-- HACK HACK HACK
+#ifdef __HUGS__
+#define INSTANCE_TYPEABLE1x(tycon,tcname,str) \
+instance Typeable a => Typeable (tycon a) where { \
+ typeOf x = mkAppTy tcname [typeOf ((undefined :: tycon a -> a) x) ] }
+#define INSTANCE_TYPEABLE2x(tycon,tcname,str) \
+instance (Typeable a, Typeable b) => Typeable (tycon a b) where { \
+ typeOf x = mkAppTy tcname [typeOf ((undefined :: tycon a b -> a) x), \
+ typeOf ((undefined :: tycon a b -> b) x)] }
+
+INSTANCE_TYPEABLE1x(Ratio,ratioTc,"Ratio")
+INSTANCE_TYPEABLE2x(Either,eitherTc,"Either")
+INSTANCE_TYPEABLE1(IO,ioTc,"IO")
+INSTANCE_TYPEABLE1x(Maybe,maybeTc,"Maybe")
+INSTANCE_TYPEABLE1(Ptr,ptrTc,"Ptr")
+INSTANCE_TYPEABLE1(StablePtr,stablePtrTc,"StablePtr")
+INSTANCE_TYPEABLE1(IORef,ioRefTc,"IORef")
+#endif
+
+-- | Variant for unary type constructors
+class Typeable1 t where
+ typeOf1 :: t a -> TypeRep
+
+
+#ifndef __HUGS__
+-- | One Typeable instance for all Typeable1 instances
+instance (Typeable1 s, Typeable a)
+ => Typeable (s a) where
+ typeOf x = typeOf1 x `popStarTy` typeOf (argType x)
+ where
+ argType :: t x -> x
+ argType = undefined
+#endif
+
+
+-- | Variant for binary type constructors
+class Typeable2 t where
+ typeOf2 :: t a b -> TypeRep
+
+
+#ifndef __HUGS__
+-- | One Typeable1 instance for all Typeable2 instances
+instance (Typeable2 s, Typeable a)
+ => Typeable1 (s a) where
+ typeOf1 x = typeOf2 x `popStarTy` typeOf (argType x)
+ where
+ argType :: t x y -> x
+ argType = undefined
+#endif
+
+
+-- | Variant for 3-ary type constructors
+class Typeable3 t where
+ typeOf3 :: t a b c -> TypeRep
+
+
+#ifndef __HUGS__
+-- | One Typeable2 instance for all Typeable3 instances
+instance (Typeable3 s, Typeable a)
+ => Typeable2 (s a) where
+ typeOf2 x = typeOf3 x `popStarTy` typeOf (argType x)
+ where
+ argType :: t x y z -> x
+ argType = undefined
+#endif
+
+
+-- | Variant for 4-ary type constructors
+class Typeable4 t where
+ typeOf4 :: t a b c d -> TypeRep
+
+
+#ifndef __HUGS__
+-- | One Typeable3 instance for all Typeable4 instances
+instance (Typeable4 s, Typeable a)
+ => Typeable3 (s a) where
+ typeOf3 x = typeOf4 x `popStarTy` typeOf (argType x)
+ where
+ argType :: t x y z z' -> x
+ argType = undefined
+#endif
+
+
+-- | Variant for 5-ary type constructors
+class Typeable5 t where
+ typeOf5 :: t a b c d e -> TypeRep
+
+
+#ifndef __HUGS__
+-- | One Typeable4 instance for all Typeable5 instances
+instance (Typeable5 s, Typeable a)
+ => Typeable4 (s a) where
+ typeOf4 x = typeOf5 x `popStarTy` typeOf (argType x)
+ where
+ argType :: t x y z z' z'' -> x
+ argType = undefined
+#endif
+
+
+-- | Variant for 6-ary type constructors
+class Typeable6 t where
+ typeOf6 :: t a b c d e f -> TypeRep
+
+
+#ifndef __HUGS__
+-- | One Typeable5 instance for all Typeable6 instances
+instance (Typeable6 s, Typeable a)
+ => Typeable5 (s a) where
+ typeOf5 x = typeOf6 x `popStarTy` typeOf (argType x)
+ where
+ argType :: t x y z z' z'' z''' -> x
+ argType = undefined
+#endif
+
+
+-- | Variant for 7-ary type constructors
+class Typeable7 t where
+ typeOf7 :: t a b c d e f g -> TypeRep
+
+
+#ifndef __HUGS__
+-- | One Typeable6 instance for all Typeable7 instances
+instance (Typeable7 s, Typeable a)
+ => Typeable6 (s a) where
+ typeOf6 x = typeOf7 x `popStarTy` typeOf (argType x)
+ where
+ argType :: t x y z z' z'' z''' z'''' -> x
+ argType = undefined
+#endif
+
+
-------------------------------------------------------------
--
else Nothing
--- | A convenient variation for kind \"* -> *\"
-castss :: (Typeable a, Typeable b) => t a -> Maybe (t b)
-castss x = r
- where
- r = if typeOf (get x) == typeOf (get (fromJust r))
- then Just $ unsafeCoerce x
- else Nothing
- get :: t c -> c
- get = undefined
+-- | A flexible variation parameterised in a type constructor
+gcast :: (Typeable a, Typeable b) => c a -> Maybe (c b)
+gcast x = r
+ where
+ r = if typeOf (getArg x) == typeOf (getArg (fromJust r))
+ then Just $ unsafeCoerce x
+ else Nothing
+ getArg :: c x -> x
+ getArg = undefined
--- | Another variation
-castarr :: (Typeable a, Typeable b, Typeable c, Typeable d)
- => (a -> t b) -> Maybe (c -> t d)
-castarr x = r
- where
- r = if typeOf (get x) == typeOf (get (fromJust r))
- then Just $ unsafeCoerce x
- else Nothing
- get :: (e -> t f) -> (e, f)
- get = undefined
-{-
+-- | Cast for * -> *
+gcast1 :: (Typeable1 t, Typeable1 t') => c (t a) -> Maybe (c (t' a))
+gcast1 x = r
+ where
+ r = if typeOf1 (getArg x) == typeOf1 (getArg (fromJust r))
+ then Just $ unsafeCoerce x
+ else Nothing
+ getArg :: c x -> x
+ getArg = undefined
+
-The variations castss and castarr are arguably not really needed.
-Let's discuss castss in some detail. To get rid of castss, we can
-require "Typeable (t a)" and "Typeable (t b)" rather than just
-"Typeable a" and "Typeable b". In that case, the ordinary cast would
-work. Eventually, all kinds of library instances should become
-Typeable. (There is another potential use of variations as those given
-above. It allows quantification on type constructors.
+-- | Cast for * -> * -> *
+gcast2 :: (Typeable2 t, Typeable2 t') => c (t a b) -> Maybe (c (t' a b))
+gcast2 x = r
+ where
+ r = if typeOf2 (getArg x) == typeOf2 (getArg (fromJust r))
+ then Just $ unsafeCoerce x
+ else Nothing
+ getArg :: c x -> x
+ getArg = undefined
--}
-------------------------------------------------------------
--
--- Instances of the Typeable class for Prelude types
+-- Instances of the Typeable classes for Prelude types
--
-------------------------------------------------------------
-listTc :: TyCon
-listTc = mkTyCon "[]"
-
-instance Typeable a => Typeable [a] where
- typeOf ls = mkAppTy listTc [typeOf ((undefined :: [a] -> a) ls)]
- -- In GHC we can say
- -- typeOf (undefined :: a)
- -- using scoped type variables, but we use the
- -- more verbose form here, for compatibility with Hugs
-
unitTc :: TyCon
unitTc = mkTyCon "()"
instance Typeable () where
typeOf _ = mkAppTy unitTc []
-tup2Tc :: TyCon
-tup2Tc = mkTyCon ","
-
-instance (Typeable a, Typeable b) => Typeable (a,b) where
- typeOf tu = mkAppTy tup2Tc [typeOf ((undefined :: (a,b) -> a) tu),
- typeOf ((undefined :: (a,b) -> b) tu)]
tup3Tc :: TyCon
tup3Tc = mkTyCon ",,"
-instance ( Typeable a , Typeable b , Typeable c) => Typeable (a,b,c) where
- typeOf tu = mkAppTy tup3Tc [typeOf ((undefined :: (a,b,c) -> a) tu),
- typeOf ((undefined :: (a,b,c) -> b) tu),
- typeOf ((undefined :: (a,b,c) -> c) tu)]
+instance Typeable3 (,,) where
+ typeOf3 tu = mkAppTy tup3Tc []
+
tup4Tc :: TyCon
tup4Tc = mkTyCon ",,,"
-instance ( Typeable a
- , Typeable b
- , Typeable c
- , Typeable d) => Typeable (a,b,c,d) where
- typeOf tu = mkAppTy tup4Tc [typeOf ((undefined :: (a,b,c,d) -> a) tu),
- typeOf ((undefined :: (a,b,c,d) -> b) tu),
- typeOf ((undefined :: (a,b,c,d) -> c) tu),
- typeOf ((undefined :: (a,b,c,d) -> d) tu)]
+instance Typeable4 (,,,) where
+ typeOf4 tu = mkAppTy tup4Tc []
+
+
tup5Tc :: TyCon
tup5Tc = mkTyCon ",,,,"
-instance ( Typeable a
- , Typeable b
- , Typeable c
- , Typeable d
- , Typeable e) => Typeable (a,b,c,d,e) where
- typeOf tu = mkAppTy tup5Tc [typeOf ((undefined :: (a,b,c,d,e) -> a) tu),
- typeOf ((undefined :: (a,b,c,d,e) -> b) tu),
- typeOf ((undefined :: (a,b,c,d,e) -> c) tu),
- typeOf ((undefined :: (a,b,c,d,e) -> d) tu),
- typeOf ((undefined :: (a,b,c,d,e) -> e) tu)]
+instance Typeable5 (,,,,) where
+ typeOf5 tu = mkAppTy tup5Tc []
+
+
+tup6Tc :: TyCon
+tup6Tc = mkTyCon ",,,,,"
+
+instance Typeable6 (,,,,,) where
+ typeOf6 tu = mkAppTy tup6Tc []
+
+
+tup7Tc :: TyCon
+tup7Tc = mkTyCon ",,,,,"
+
+instance Typeable7 (,,,,,,) where
+ typeOf7 tu = mkAppTy tup7Tc []
+
+
+listTc :: TyCon
+listTc = mkTyCon "[]"
+
+-- | Instance for lists
+instance Typeable1 [] where
+ typeOf1 _ = mkAppTy listTc []
+
+
+maybeTc :: TyCon
+maybeTc = mkTyCon "Maybe"
+
+-- | Instance for maybes
+instance Typeable1 Maybe where
+ typeOf1 _ = mkAppTy maybeTc []
+
-instance (Typeable a, Typeable b) => Typeable (a -> b) where
- typeOf f = mkFunTy (typeOf ((undefined :: (a -> b) -> a) f))
- (typeOf ((undefined :: (a -> b) -> b) f))
+ratioTc :: TyCon
+ratioTc = mkTyCon "Ratio"
+
+-- | Instance for ratios
+instance Typeable1 Ratio where
+ typeOf1 _ = mkAppTy ratioTc []
+
+
+pairTc :: TyCon
+pairTc = mkTyCon "(,)"
+
+-- | Instance for products
+instance Typeable2 (,) where
+ typeOf2 _ = mkAppTy pairTc []
+
+
+eitherTc :: TyCon
+eitherTc = mkTyCon "Either"
+
+-- | Instance for sums
+instance Typeable2 Either where
+ typeOf2 _ = mkAppTy eitherTc []
+
+
+-- | Instance for functions
+instance Typeable2 (->) where
+ typeOf2 _ = mkAppTy funTc []
+
+
+#ifdef __GLASGOW_HASKELL__
+
+ioTc :: TyCon
+ioTc = mkTyCon "GHC.IOBase.IO"
+
+instance Typeable1 IO where
+ typeOf1 _ = mkAppTy ioTc []
+
+
+ptrTc :: TyCon
+ptrTc = mkTyCon "GHC.Ptr.Ptr"
+
+instance Typeable1 Ptr where
+ typeOf1 _ = mkAppTy ptrTc []
+
+
+stableptrTc :: TyCon
+stableptrTc = mkTyCon "GHC.Stable.StablePtr"
+
+instance Typeable1 StablePtr where
+ typeOf1 _ = mkAppTy stableptrTc []
+
+
+iorefTc :: TyCon
+iorefTc = mkTyCon "GHC.IOBase.IORef"
+
+instance Typeable1 IORef where
+ typeOf1 _ = mkAppTy iorefTc []
+
+#endif
INSTANCE_TYPEABLE0(Double,doubleTc,"Double")
INSTANCE_TYPEABLE0(Int,intTc,"Int")
INSTANCE_TYPEABLE0(Integer,integerTc,"Integer")
-INSTANCE_TYPEABLE1(Ratio,ratioTc,"Ratio")
-INSTANCE_TYPEABLE2(Either,eitherTc,"Either")
-INSTANCE_TYPEABLE1(IO,ioTc,"IO")
-INSTANCE_TYPEABLE1(Maybe,maybeTc,"Maybe")
INSTANCE_TYPEABLE0(Ordering,orderingTc,"Ordering")
INSTANCE_TYPEABLE0(Handle,handleTc,"Handle")
-INSTANCE_TYPEABLE1(Ptr,ptrTc,"Ptr")
-INSTANCE_TYPEABLE1(StablePtr,stablePtrTc,"StablePtr")
INSTANCE_TYPEABLE0(Int8,int8Tc,"Int8")
INSTANCE_TYPEABLE0(Int16,int16Tc,"Int16")
INSTANCE_TYPEABLE0(TyCon,tyconTc,"TyCon")
INSTANCE_TYPEABLE0(TypeRep,typeRepTc,"TypeRep")
+#endif
-INSTANCE_TYPEABLE1(IORef,ioRefTc,"IORef")
+#ifdef __GLASGOW_HASKELL__
+INSTANCE_TYPEABLE0(Word,wordTc,"Word" )
#endif
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