#ifdef __GLASGOW_HASKELL__
#endif
module Data.Dynamic
(
module Data.Typeable,
Dynamic,
toDyn,
fromDyn,
fromDynamic,
dynApply,
dynApp,
dynTypeRep
) where
import Data.Typeable
import Data.Maybe
import Unsafe.Coerce
#ifdef __GLASGOW_HASKELL__
import GHC.Base
import GHC.Show
import GHC.Exception
#endif
#ifdef __HUGS__
import Hugs.Prelude
import Hugs.IO
import Hugs.IORef
import Hugs.IOExts
#endif
#ifdef __NHC__
import NHC.IOExtras (IORef,newIORef,readIORef,writeIORef,unsafePerformIO)
#endif
#include "Typeable.h"
#ifndef __HUGS__
data Dynamic = Dynamic TypeRep Obj
#endif
INSTANCE_TYPEABLE0(Dynamic,dynamicTc,"Dynamic")
instance Show Dynamic where
showsPrec _ (Dynamic t _) =
showString "<<" .
showsPrec 0 t .
showString ">>"
#ifdef __GLASGOW_HASKELL__
instance Exception Dynamic
#endif
#ifdef __GLASGOW_HASKELL__
type Obj = Any
#elif !defined(__HUGS__)
data Obj = Obj
#endif
toDyn :: Typeable a => a -> Dynamic
toDyn v = Dynamic (typeOf v) (unsafeCoerce v)
fromDyn :: Typeable a
=> Dynamic
-> a
-> a
fromDyn (Dynamic t v) def
| typeOf def == t = unsafeCoerce v
| otherwise = def
fromDynamic
:: Typeable a
=> Dynamic
-> Maybe a
fromDynamic (Dynamic t v) =
case unsafeCoerce v of
r | t == typeOf r -> Just r
| otherwise -> Nothing
dynApply :: Dynamic -> Dynamic -> Maybe Dynamic
dynApply (Dynamic t1 f) (Dynamic t2 x) =
case funResultTy t1 t2 of
Just t3 -> Just (Dynamic t3 ((unsafeCoerce f) x))
Nothing -> Nothing
dynApp :: Dynamic -> Dynamic -> Dynamic
dynApp f x = case dynApply f x of
Just r -> r
Nothing -> error ("Type error in dynamic application.\n" ++
"Can't apply function " ++ show f ++
" to argument " ++ show x)
dynTypeRep :: Dynamic -> TypeRep
dynTypeRep (Dynamic tr _) = tr
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