/usr/lib/hugs/packages/base/Data/Typeable.hs is in libhugs-base-bundled 98.200609.21-5.4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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-- The -fallow-overlapping-instances flag allows the user to over-ride
-- the instances for Typeable given here. In particular, we provide an instance
-- instance ... => Typeable (s a)
-- But a user might want to say
-- instance ... => Typeable (MyType a b)
-----------------------------------------------------------------------------
-- |
-- Module : Data.Typeable
-- Copyright : (c) The University of Glasgow, CWI 2001--2004
-- License : BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer : libraries@haskell.org
-- Stability : experimental
-- Portability : portable
--
-- The 'Typeable' class reifies types to some extent by associating type
-- representations to types. These type representations can be compared,
-- and one can in turn define a type-safe cast operation. To this end,
-- an unsafe cast is guarded by a test for type (representation)
-- equivalence. The module "Data.Dynamic" uses Typeable for an
-- implementation of dynamics. The module "Data.Generics" uses Typeable
-- and type-safe cast (but not dynamics) to support the \"Scrap your
-- boilerplate\" style of generic programming.
--
-----------------------------------------------------------------------------
module Data.Typeable
(
-- * The Typeable class
Typeable( typeOf ), -- :: a -> TypeRep
-- * Type-safe cast
cast, -- :: (Typeable a, Typeable b) => a -> Maybe b
gcast, -- a generalisation of cast
-- * Type representations
TypeRep, -- abstract, instance of: Eq, Show, Typeable
TyCon, -- abstract, instance of: Eq, Show, Typeable
-- * Construction of type representations
mkTyCon, -- :: String -> TyCon
mkTyConApp, -- :: TyCon -> [TypeRep] -> TypeRep
mkAppTy, -- :: TypeRep -> TypeRep -> TypeRep
mkFunTy, -- :: TypeRep -> TypeRep -> TypeRep
-- * 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 Data.Either
import Data.Int
import Data.Word
import Data.List( foldl )
import Hugs.Prelude ( Key(..), TypeRep(..), TyCon(..), Ratio,
Exception, ArithException, IOException,
ArrayException, AsyncException, Handle,
Ptr, FunPtr, ForeignPtr, StablePtr )
import Hugs.IORef ( IORef, newIORef, readIORef, writeIORef )
import Hugs.IOExts ( unsafePerformIO, unsafeCoerce )
-- For the Typeable instance
import Hugs.Array ( Array )
import Hugs.ConcBase ( MVar )
--
-- let fTy = mkTyCon "Foo" in show (mkTyConApp (mkTyCon ",,")
-- [fTy,fTy,fTy])
--
-- returns "(Foo,Foo,Foo)"
--
-- The TypeRep Show instance promises to print tuple types
-- correctly. Tuple type constructors are specified by a
-- sequence of commas, e.g., (mkTyCon ",,,,") returns
-- the 5-tuple tycon.
----------------- Construction --------------------
-- | Applies a type constructor to a sequence of types
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]
-- | A special case of 'mkTyConApp', which applies the function
-- type constructor to a pair of types.
mkFunTy :: TypeRep -> TypeRep -> TypeRep
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'.
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,
-- we can map them onto Ints very simply. The benefit is,
-- of course, that @TyCon@s can then be compared efficiently.
-- Provided the implementor of other @Typeable@ instances
-- takes care of making all the @TyCon@s CAFs (toplevel constants),
-- this will work.
-- If this constraint does turn out to be a sore thumb, changing
-- the Eq instance for TyCons is trivial.
-- | Builds a 'TyCon' object representing a type constructor. An
-- implementation of "Data.Typeable" should ensure that the following holds:
--
-- > mkTyCon "a" == mkTyCon "a"
--
mkTyCon :: String -- ^ the name of the type constructor (should be unique
-- in the program, so it might be wise to use the
-- fully qualified name).
-> 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 --------------------
instance Show TypeRep where
showsPrec p (TypeRep _ tycon tys) =
case tys of
[] -> showsPrec p tycon
[x] | tycon == listTc -> showChar '[' . shows x . showChar ']'
[a,r] | tycon == funTc -> showParen (p > 8) $
showsPrec 9 a .
showString " -> " .
showsPrec 8 r
xs | isTupleTyCon tycon -> showTuple tycon xs
| otherwise ->
showParen (p > 9) $
showsPrec p tycon .
showChar ' ' .
showArgs tys
instance Show TyCon where
showsPrec _ (TyCon _ s) = showString s
isTupleTyCon :: TyCon -> Bool
isTupleTyCon (TyCon _ (',':_)) = True
isTupleTyCon _ = False
-- Some (Show.TypeRep) helpers:
showArgs :: Show a => [a] -> ShowS
showArgs [] = id
showArgs [a] = showsPrec 10 a
showArgs (a:as) = showsPrec 10 a . showString " " . showArgs as
showTuple :: TyCon -> [TypeRep] -> ShowS
showTuple (TyCon _ str) args = showChar '(' . go str args
where
go [] [a] = showsPrec 10 a . showChar ')'
go _ [] = showChar ')' -- a failure condition, really.
go (',':xs) (a:as) = showsPrec 10 a . showChar ',' . go xs as
go _ _ = showChar ')'
-------------------------------------------------------------
--
-- The Typeable class and friends
--
-------------------------------------------------------------
-- | The class 'Typeable' allows a concrete representation of a type to
-- be calculated.
class Typeable a where
typeOf :: a -> TypeRep
-- ^ Takes a value of type @a@ and returns a concrete representation
-- of that type. The /value/ of the argument should be ignored by
-- 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
-------------------------------------------------------------
--
-- Type-safe cast
--
-------------------------------------------------------------
-- | The type-safe cast operation
cast :: (Typeable a, Typeable b) => a -> Maybe b
cast x = r
where
r = if typeOf x == typeOf (fromJust r)
then Just $ unsafeCoerce x
else Nothing
-- | 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 classes for Prelude types
--
-------------------------------------------------------------
unitTc = mkTyCon "()"; instance Typeable () where { typeOf _ = mkTyConApp unitTc [] }
listTc = mkTyCon "[]"; instance Typeable1 [] where { typeOf1 _ = mkTyConApp listTc [] }; instance Typeable a => Typeable ([] a) where { typeOf = typeOfDefault }
maybeTc = mkTyCon "Maybe"; instance Typeable1 Maybe where { typeOf1 _ = mkTyConApp maybeTc [] }; instance Typeable a => Typeable (Maybe a) where { typeOf = typeOfDefault }
ratioTc = mkTyCon "Ratio"; instance Typeable1 Ratio where { typeOf1 _ = mkTyConApp ratioTc [] }; instance Typeable a => Typeable (Ratio a) where { typeOf = typeOfDefault }
eitherTc = mkTyCon "Either"; instance Typeable2 Either where { typeOf2 _ = mkTyConApp eitherTc [] }; instance Typeable a => Typeable1 (Either a) where { typeOf1 = typeOf1Default }; instance (Typeable a, Typeable b) => Typeable (Either a b) where { typeOf = typeOfDefault }
funTc = mkTyCon "->"; instance Typeable2 (->) where { typeOf2 _ = mkTyConApp funTc [] }; instance Typeable a => Typeable1 ((->) a) where { typeOf1 = typeOf1Default }; instance (Typeable a, Typeable b) => Typeable ((->) a b) where { typeOf = typeOfDefault }
ioTc = mkTyCon "IO"; instance Typeable1 IO where { typeOf1 _ = mkTyConApp ioTc [] }; instance Typeable a => Typeable (IO a) where { typeOf = typeOfDefault }
-- Types defined in GHC.IOBase
mvarTc = mkTyCon "MVar"; instance Typeable1 MVar where { typeOf1 _ = mkTyConApp mvarTc [] }; instance Typeable a => Typeable (MVar a) where { typeOf = typeOfDefault }
exceptionTc = mkTyCon "Exception"; instance Typeable Exception where { typeOf _ = mkTyConApp exceptionTc [] }
ioExceptionTc = mkTyCon "IOException"; instance Typeable IOException where { typeOf _ = mkTyConApp ioExceptionTc [] }
arithExceptionTc = mkTyCon "ArithException"; instance Typeable ArithException where { typeOf _ = mkTyConApp arithExceptionTc [] }
arrayExceptionTc = mkTyCon "ArrayException"; instance Typeable ArrayException where { typeOf _ = mkTyConApp arrayExceptionTc [] }
asyncExceptionTc = mkTyCon "AsyncException"; instance Typeable AsyncException where { typeOf _ = mkTyConApp asyncExceptionTc [] }
-- Types defined in GHC.Arr
arrayTc = mkTyCon "Array"; instance Typeable2 Array where { typeOf2 _ = mkTyConApp arrayTc [] }; instance Typeable a => Typeable1 (Array a) where { typeOf1 = typeOf1Default }; instance (Typeable a, Typeable b) => Typeable (Array a b) where { typeOf = typeOfDefault }
pairTc = mkTyCon ","; instance Typeable2 (,) where { typeOf2 _ = mkTyConApp pairTc [] }; instance Typeable a => Typeable1 ((,) a) where { typeOf1 = typeOf1Default }; instance (Typeable a, Typeable b) => Typeable ((,) a b) where { typeOf = typeOfDefault }
tup3Tc = mkTyCon ",,"; instance Typeable3 (,,) where { typeOf3 _ = mkTyConApp tup3Tc [] }; instance Typeable a => Typeable2 ((,,) a) where { typeOf2 = typeOf2Default }; instance (Typeable a, Typeable b) => Typeable1 ((,,) a b) where { typeOf1 = typeOf1Default }; instance (Typeable a, Typeable b, Typeable c) => Typeable ((,,) a b c) where { typeOf = typeOfDefault }
tup4Tc :: TyCon
tup4Tc = mkTyCon ",,,"
instance Typeable4 (,,,) where
typeOf4 tu = mkTyConApp tup4Tc []
tup5Tc :: TyCon
tup5Tc = mkTyCon ",,,,"
instance Typeable5 (,,,,) where
typeOf5 tu = mkTyConApp tup5Tc []
tup6Tc :: TyCon
tup6Tc = mkTyCon ",,,,,"
instance Typeable6 (,,,,,) where
typeOf6 tu = mkTyConApp tup6Tc []
tup7Tc :: TyCon
tup7Tc = mkTyCon ",,,,,,"
instance Typeable7 (,,,,,,) where
typeOf7 tu = mkTyConApp tup7Tc []
ptrTc = mkTyCon "Ptr"; instance Typeable1 Ptr where { typeOf1 _ = mkTyConApp ptrTc [] }; instance Typeable a => Typeable (Ptr a) where { typeOf = typeOfDefault }
funPtrTc = mkTyCon "FunPtr"; instance Typeable1 FunPtr where { typeOf1 _ = mkTyConApp funPtrTc [] }; instance Typeable a => Typeable (FunPtr a) where { typeOf = typeOfDefault }
foreignPtrTc = mkTyCon "ForeignPtr"; instance Typeable1 ForeignPtr where { typeOf1 _ = mkTyConApp foreignPtrTc [] }; instance Typeable a => Typeable (ForeignPtr a) where { typeOf = typeOfDefault }
stablePtrTc = mkTyCon "StablePtr"; instance Typeable1 StablePtr where { typeOf1 _ = mkTyConApp stablePtrTc [] }; instance Typeable a => Typeable (StablePtr a) where { typeOf = typeOfDefault }
iORefTc = mkTyCon "IORef"; instance Typeable1 IORef where { typeOf1 _ = mkTyConApp iORefTc [] }; instance Typeable a => Typeable (IORef a) where { typeOf = typeOfDefault }
-------------------------------------------------------
--
-- Generate Typeable instances for standard datatypes
--
-------------------------------------------------------
boolTc = mkTyCon "Bool"; instance Typeable Bool where { typeOf _ = mkTyConApp boolTc [] }
charTc = mkTyCon "Char"; instance Typeable Char where { typeOf _ = mkTyConApp charTc [] }
floatTc = mkTyCon "Float"; instance Typeable Float where { typeOf _ = mkTyConApp floatTc [] }
doubleTc = mkTyCon "Double"; instance Typeable Double where { typeOf _ = mkTyConApp doubleTc [] }
intTc = mkTyCon "Int"; instance Typeable Int where { typeOf _ = mkTyConApp intTc [] }
wordTc = mkTyCon "Word"; instance Typeable Word where { typeOf _ = mkTyConApp wordTc [] }
integerTc = mkTyCon "Integer"; instance Typeable Integer where { typeOf _ = mkTyConApp integerTc [] }
orderingTc = mkTyCon "Ordering"; instance Typeable Ordering where { typeOf _ = mkTyConApp orderingTc [] }
handleTc = mkTyCon "Handle"; instance Typeable Handle where { typeOf _ = mkTyConApp handleTc [] }
int8Tc = mkTyCon "Int8"; instance Typeable Int8 where { typeOf _ = mkTyConApp int8Tc [] }
int16Tc = mkTyCon "Int16"; instance Typeable Int16 where { typeOf _ = mkTyConApp int16Tc [] }
int32Tc = mkTyCon "Int32"; instance Typeable Int32 where { typeOf _ = mkTyConApp int32Tc [] }
int64Tc = mkTyCon "Int64"; instance Typeable Int64 where { typeOf _ = mkTyConApp int64Tc [] }
word8Tc = mkTyCon "Word8"; instance Typeable Word8 where { typeOf _ = mkTyConApp word8Tc [] }
word16Tc = mkTyCon "Word16"; instance Typeable Word16 where { typeOf _ = mkTyConApp word16Tc [] }
word32Tc = mkTyCon "Word32"; instance Typeable Word32 where { typeOf _ = mkTyConApp word32Tc [] }
word64Tc = mkTyCon "Word64"; instance Typeable Word64 where { typeOf _ = mkTyConApp word64Tc [] }
tyconTc = mkTyCon "TyCon"; instance Typeable TyCon where { typeOf _ = mkTyConApp tyconTc [] }
typeRepTc = mkTyCon "TypeRep"; instance Typeable TypeRep where { typeOf _ = mkTyConApp typeRepTc [] }
---------------------------------------------
--
-- Internals
--
---------------------------------------------
data KeyPr = KeyPr !Key !Key deriving( Eq )
hashKP :: KeyPr -> Int32
hashKP (KeyPr (Key k1) (Key k2)) = (HT.hashInt k1 + HT.hashInt k2) `rem` HT.prime
data Cache = Cache { next_key :: !(IORef Key), -- Not used by GHC (calls genSym instead)
tc_tbl :: !(HT.HashTable String Key),
ap_tbl :: !(HT.HashTable KeyPr Key) }
{-# NOINLINE cache #-}
cache :: Cache
cache = unsafePerformIO $ do
empty_tc_tbl <- HT.new (==) HT.hashString
empty_ap_tbl <- HT.new (==) hashKP
key_loc <- newIORef (Key 1)
let ret = Cache { next_key = key_loc,
tc_tbl = empty_tc_tbl,
ap_tbl = empty_ap_tbl }
return ret
newKey :: IORef Key -> IO Key
newKey kloc = do { k@(Key i) <- readIORef kloc ;
writeIORef kloc (Key (i+1)) ;
return k }
mkTyConKey :: String -> Key
mkTyConKey str
= unsafePerformIO $ do
let Cache {next_key = kloc, tc_tbl = tbl} = cache
mb_k <- HT.lookup tbl str
case mb_k of
Just k -> return k
Nothing -> do { k <- newKey kloc ;
HT.insert tbl str k ;
return k }
appKey :: Key -> Key -> Key
appKey k1 k2
= unsafePerformIO $ do
let Cache {next_key = kloc, ap_tbl = tbl} = cache
mb_k <- HT.lookup tbl kpr
case mb_k of
Just k -> return k
Nothing -> do { k <- newKey kloc ;
HT.insert tbl kpr k ;
return k }
where
kpr = KeyPr k1 k2
appKeys :: Key -> [Key] -> Key
appKeys k ks = foldl appKey k ks
|