-{-# OPTIONS -fno-implicit-prelude #-}
+{-# OPTIONS_GHC -fno-implicit-prelude #-}
-----------------------------------------------------------------------------
-- |
-- Module : Data.Dynamic
-- * Applying functions of dynamic type
dynApply,
- dynApp
+ dynApp,
+ dynTypeRep
) where
import GHC.Show
import GHC.Err
import GHC.Num
-import GHC.Float
-import GHC.Real( rem )
-import GHC.IOBase
#endif
#ifdef __HUGS__
#ifdef __NHC__
import NonStdUnsafeCoerce (unsafeCoerce)
import NHC.IOExtras (IORef,newIORef,readIORef,writeIORef,unsafePerformIO)
-#else
-#include "Typeable.h"
#endif
+#include "Typeable.h"
+
-------------------------------------------------------------
--
-- The type Dynamic
data Dynamic = Dynamic TypeRep Obj
#endif
-#ifndef __NHC__
INSTANCE_TYPEABLE0(Dynamic,dynamicTc,"Dynamic")
-#endif
instance Show Dynamic where
-- the instance just prints the type representation.
fromDynamic
:: Typeable a
=> Dynamic -- ^ the dynamically-typed object
- -> Maybe a -- ^ returns: @'Just' a@, if the dyanmically-typed
+ -> Maybe a -- ^ returns: @'Just' a@, if the dynamically-typed
-- object has the correct type (and @a@ is its value),
-- or 'Nothing' otherwise.
fromDynamic (Dynamic t v) =
-- (f::(a->b)) `dynApply` (x::a) = (f a)::b
dynApply :: Dynamic -> Dynamic -> Maybe Dynamic
dynApply (Dynamic t1 f) (Dynamic t2 x) =
- case applyTy t1 t2 of
+ case funResultTy t1 t2 of
Just t3 -> Just (Dynamic t3 ((unsafeCoerce f) x))
Nothing -> Nothing
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