-----------------------------------------------------------------------------
-- |
-- 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
-- * Construction of type representations
mkTyCon, -- :: String -> TyCon
- mkAppTy, -- :: TyCon -> [TypeRep] -> TypeRep
+ mkTyConApp, -- :: TyCon -> [TypeRep] -> TypeRep
+ mkAppTy, -- :: TypeRep -> TypeRep -> TypeRep
mkFunTy, -- :: TypeRep -> TypeRep -> TypeRep
- applyTy -- :: TypeRep -> TypeRep -> Maybe TypeRep
- ) where
+ -- * Observation of type representations
+ splitTyConApp, -- :: TypeRep -> (TyCon, [TypeRep])
+ funResultTy, -- :: TypeRep -> TypeRep -> Maybe TypeRep
+ typeRepTyCon, -- :: TypeRep -> TyCon
+ typeRepArgs, -- :: TypeRep -> [TypeRep]
+ tyConString, -- :: TyCon -> String
+
+ -- * The other Typeable classes
+ -- | /Note:/ The general instances are provided for GHC only.
+ 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))
+
+ -- * Default instances
+ -- | /Note:/ These are not needed by GHC, for which these instances
+ -- are generated by general instance declarations.
+ typeOfDefault, -- :: (Typeable1 t, Typeable a) => t a -> TypeRep
+ typeOf1Default, -- :: (Typeable2 t, Typeable a) => t a b -> TypeRep
+ typeOf2Default, -- :: (Typeable3 t, Typeable a) => t a b c -> TypeRep
+ typeOf3Default, -- :: (Typeable4 t, Typeable a) => t a b c d -> TypeRep
+ typeOf4Default, -- :: (Typeable5 t, Typeable a) => t a b c d e -> TypeRep
+ typeOf5Default, -- :: (Typeable6 t, Typeable a) => t a b c d e f -> TypeRep
+ typeOf6Default -- :: (Typeable7 t, Typeable a) => t a b c d e f g -> TypeRep
+ ) where
import qualified Data.HashTable as HT
import Data.Maybe
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__
#ifdef __NHC__
import NonStdUnsafeCoerce (unsafeCoerce)
import NHC.IOExtras (IORef,newIORef,readIORef,writeIORef,unsafePerformIO)
+import IO (Handle)
+import Ratio (Ratio)
+import NHC.FFI (Ptr,StablePtr)
#else
-#include "Typeable.h"
#endif
+#include "Typeable.h"
#ifndef __HUGS__
+
-------------------------------------------------------------
--
-- Type representations
--
-------------------------------------------------------------
-
-- | A concrete representation of a (monomorphic) type. 'TypeRep'
-- supports reasonably efficient equality.
data TypeRep = TypeRep !Key TyCon [TypeRep]
#endif
--
- -- let fTy = mkTyCon "Foo" in show (mkAppTy (mkTyCon ",,")
+ -- let fTy = mkTyCon "Foo" in show (mkTyConApp (mkTyCon ",,")
-- [fTy,fTy,fTy])
--
-- returns "(Foo,Foo,Foo)"
----------------- Construction --------------------
-- | Applies a type constructor to a sequence of types
-mkAppTy :: TyCon -> [TypeRep] -> TypeRep
-mkAppTy tc@(TyCon tc_k _) args
+mkTyConApp :: TyCon -> [TypeRep] -> TypeRep
+mkTyConApp tc@(TyCon tc_k _) args
= TypeRep (appKeys tc_k arg_ks) tc args
where
arg_ks = [k | TypeRep k _ _ <- args]
-funTc :: TyCon
-funTc = mkTyCon "->"
-
--- | A special case of 'mkAppTy', which applies the function
+-- | A special case of 'mkTyConApp', which applies the function
-- type constructor to a pair of types.
mkFunTy :: TypeRep -> TypeRep -> TypeRep
-mkFunTy f a = mkAppTy funTc [f,a]
+mkFunTy f a = mkTyConApp funTc [f,a]
+
+-- | Splits a type constructor application
+splitTyConApp :: TypeRep -> (TyCon,[TypeRep])
+splitTyConApp (TypeRep _ tc trs) = (tc,trs)
-- | 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,
-- returns 'Nothing'.
-applyTy :: TypeRep -> TypeRep -> Maybe TypeRep
-applyTy (TypeRep _ tc [t1,t2]) t3
- | tc == funTc && t1 == t3 = Just t2
-applyTy _ _ = Nothing
+funResultTy :: TypeRep -> TypeRep -> Maybe TypeRep
+funResultTy trFun trArg
+ = case splitTyConApp trFun of
+ (tc, [t1,t2]) | tc == funTc && t1 == trArg -> Just t2
+ _ -> Nothing
+
+-- | Adds a TypeRep argument to a TypeRep.
+mkAppTy :: TypeRep -> TypeRep -> TypeRep
+mkAppTy (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,
-> TyCon -- ^ A unique 'TyCon' object
mkTyCon str = TyCon (mkTyConKey str) str
+----------------- Observation ---------------------
+
+-- | Observe the type constructor of a type representation
+typeRepTyCon :: TypeRep -> TyCon
+typeRepTyCon (TypeRep _ tc _) = tc
+
+-- | Observe the argument types of a type representation
+typeRepArgs :: TypeRep -> [TypeRep]
+typeRepArgs (TypeRep _ _ args) = args
+-- | Observe string encoding of a type representation
+tyConString :: TyCon -> String
+tyConString (TyCon _ str) = str
----------------- Showing TypeReps --------------------
[] -> 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) $
go (',':xs) (a:as) = showsPrec 10 a . showChar ',' . go xs as
go _ _ = showChar ')'
-
-------------------------------------------------------------
--
--- The Typeable class
+-- The Typeable class and friends
--
-------------------------------------------------------------
-- any instance of 'Typeable', so that it is safe to pass 'undefined' as
-- the argument.
+-- | Variant for unary type constructors
+class Typeable1 t where
+ typeOf1 :: t a -> TypeRep
+
+-- | For defining a 'Typeable' instance from any 'Typeable1' instance.
+typeOfDefault :: (Typeable1 t, Typeable a) => t a -> TypeRep
+typeOfDefault x = typeOf1 x `mkAppTy` typeOf (argType x)
+ where
+ argType :: t a -> a
+ argType = undefined
+
+-- | Variant for binary type constructors
+class Typeable2 t where
+ typeOf2 :: t a b -> TypeRep
+
+-- | For defining a 'Typeable1' instance from any 'Typeable2' instance.
+typeOf1Default :: (Typeable2 t, Typeable a) => t a b -> TypeRep
+typeOf1Default x = typeOf2 x `mkAppTy` typeOf (argType x)
+ where
+ argType :: t a b -> a
+ argType = undefined
+
+-- | Variant for 3-ary type constructors
+class Typeable3 t where
+ typeOf3 :: t a b c -> TypeRep
+
+-- | For defining a 'Typeable2' instance from any 'Typeable3' instance.
+typeOf2Default :: (Typeable3 t, Typeable a) => t a b c -> TypeRep
+typeOf2Default x = typeOf3 x `mkAppTy` typeOf (argType x)
+ where
+ argType :: t a b c -> a
+ argType = undefined
+
+-- | Variant for 4-ary type constructors
+class Typeable4 t where
+ typeOf4 :: t a b c d -> TypeRep
+
+-- | For defining a 'Typeable3' instance from any 'Typeable4' instance.
+typeOf3Default :: (Typeable4 t, Typeable a) => t a b c d -> TypeRep
+typeOf3Default x = typeOf4 x `mkAppTy` typeOf (argType x)
+ where
+ argType :: t a b c d -> a
+ argType = undefined
+
+-- | Variant for 5-ary type constructors
+class Typeable5 t where
+ typeOf5 :: t a b c d e -> TypeRep
+
+-- | For defining a 'Typeable4' instance from any 'Typeable5' instance.
+typeOf4Default :: (Typeable5 t, Typeable a) => t a b c d e -> TypeRep
+typeOf4Default x = typeOf5 x `mkAppTy` typeOf (argType x)
+ where
+ argType :: t a b c d e -> a
+ argType = undefined
+
+-- | Variant for 6-ary type constructors
+class Typeable6 t where
+ typeOf6 :: t a b c d e f -> TypeRep
+
+-- | For defining a 'Typeable5' instance from any 'Typeable6' instance.
+typeOf5Default :: (Typeable6 t, Typeable a) => t a b c d e f -> TypeRep
+typeOf5Default x = typeOf6 x `mkAppTy` typeOf (argType x)
+ where
+ argType :: t a b c d e f -> a
+ argType = undefined
+
+-- | Variant for 7-ary type constructors
+class Typeable7 t where
+ typeOf7 :: t a b c d e f g -> TypeRep
+
+-- | For defining a 'Typeable6' instance from any 'Typeable7' instance.
+typeOf6Default :: (Typeable7 t, Typeable a) => t a b c d e f g -> TypeRep
+typeOf6Default x = typeOf7 x `mkAppTy` typeOf (argType x)
+ where
+ argType :: t a b c d e f g -> a
+ argType = undefined
+
+#ifdef __GLASGOW_HASKELL__
+-- Given a @Typeable@/n/ instance for an /n/-ary type constructor,
+-- define the instances for partial applications.
+-- Programmers using non-GHC implementations must do this manually
+-- for each type constructor.
+-- (The INSTANCE_TYPEABLE/n/ macros in Typeable.h include this.)
+
+-- | One Typeable instance for all Typeable1 instances
+instance (Typeable1 s, Typeable a)
+ => Typeable (s a) where
+ typeOf = typeOfDefault
+
+-- | One Typeable1 instance for all Typeable2 instances
+instance (Typeable2 s, Typeable a)
+ => Typeable1 (s a) where
+ typeOf1 = typeOf1Default
+
+-- | One Typeable2 instance for all Typeable3 instances
+instance (Typeable3 s, Typeable a)
+ => Typeable2 (s a) where
+ typeOf2 = typeOf2Default
+
+-- | One Typeable3 instance for all Typeable4 instances
+instance (Typeable4 s, Typeable a)
+ => Typeable3 (s a) where
+ typeOf3 = typeOf3Default
+
+-- | One Typeable4 instance for all Typeable5 instances
+instance (Typeable5 s, Typeable a)
+ => Typeable4 (s a) where
+ typeOf4 = typeOf4Default
+
+-- | One Typeable5 instance for all Typeable6 instances
+instance (Typeable6 s, Typeable a)
+ => Typeable5 (s a) where
+ typeOf5 = typeOf5Default
+
+-- | One Typeable6 instance for all Typeable7 instances
+instance (Typeable7 s, Typeable a)
+ => Typeable6 (s a) where
+ typeOf6 = typeOf6Default
+
+#endif /* __GLASGOW_HASKELL__ */
-------------------------------------------------------------
--
then Just $ unsafeCoerce x
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
-
-
--- | 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
-
-{-
-
-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.
-
--}
-
+-- | 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
+
+-- | 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
+
+-- | 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_TYPEABLE1([],listTc,"[]")
+INSTANCE_TYPEABLE1(Maybe,maybeTc,"Maybe")
+INSTANCE_TYPEABLE1(Ratio,ratioTc,"Ratio")
+INSTANCE_TYPEABLE2(Either,eitherTc,"Either")
+INSTANCE_TYPEABLE2((->),funTc,"->")
+INSTANCE_TYPEABLE1(IO,ioTc,"IO")
+INSTANCE_TYPEABLE0((),unitTc,"()")
+#ifndef __NHC__
+INSTANCE_TYPEABLE2((,),pairTc,",")
+INSTANCE_TYPEABLE3((,,),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 = mkTyConApp 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 = mkTyConApp tup5Tc []
+
+tup6Tc :: TyCon
+tup6Tc = mkTyCon ",,,,,"
-instance (Typeable a, Typeable b) => Typeable (a -> b) where
- typeOf f = mkFunTy (typeOf ((undefined :: (a -> b) -> a) f))
- (typeOf ((undefined :: (a -> b) -> b) f))
+instance Typeable6 (,,,,,) where
+ typeOf6 tu = mkTyConApp tup6Tc []
+tup7Tc :: TyCon
+tup7Tc = mkTyCon ",,,,,"
+instance Typeable7 (,,,,,,) where
+ typeOf7 tu = mkTyConApp tup7Tc []
+
+#endif /* __NHC__ */
+INSTANCE_TYPEABLE1(Ptr,ptrTc,"Ptr")
+INSTANCE_TYPEABLE1(StablePtr,stableptrTc,"StablePtr")
+INSTANCE_TYPEABLE1(IORef,iorefTc,"IORef")
-------------------------------------------------------
--
--
-------------------------------------------------------
-#ifndef __NHC__
INSTANCE_TYPEABLE0(Bool,boolTc,"Bool")
INSTANCE_TYPEABLE0(Char,charTc,"Char")
INSTANCE_TYPEABLE0(Float,floatTc,"Float")
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")
-INSTANCE_TYPEABLE1(IORef,ioRefTc,"IORef")
+#ifdef __GLASGOW_HASKELL__
+INSTANCE_TYPEABLE0(Word,wordTc,"Word" )
#endif
-
-
---------------------------------------------
--
-- Internals