#include "gadts.h"
module Darcs.Sealed ( Sealed(..), seal, unseal, mapSeal,
#ifndef GADT_WITNESSES
unsafeUnseal, unsafeUnflippedseal, unsafeUnseal2,
#endif
Sealed2(..), seal2, unseal2, mapSeal2,
FlippedSeal(..), flipSeal, unsealFlipped, mapFlipped,
unsealM, liftSM
) where
import GHC.Base ( unsafeCoerce# )
import Darcs.Show
data Sealed a where
Sealed :: a C(x ) -> Sealed a
seal :: a C(x ) -> Sealed a
seal = Sealed
data Sealed2 a where
Sealed2 :: !(a C(x y )) -> Sealed2 a
seal2 :: a C(x y ) -> Sealed2 a
seal2 = Sealed2
data FlippedSeal a C(y) where
FlippedSeal :: !(a C(x y)) -> FlippedSeal a C(y)
flipSeal :: a C(x y) -> FlippedSeal a C(y)
flipSeal = FlippedSeal
#ifndef GADT_WITNESSES
unsafeUnseal :: Sealed a -> a
unsafeUnseal (Sealed a) = a
unsafeUnflippedseal :: FlippedSeal a -> a
unsafeUnflippedseal (FlippedSeal a) = a
unsafeUnseal2 :: Sealed2 a -> a
unsafeUnseal2 (Sealed2 a) = a
#endif
seriouslyUnsafeUnseal :: Sealed a -> a C(())
seriouslyUnsafeUnseal (Sealed a) = unsafeCoerce# a
unseal :: (FORALL(x) a C(x ) -> b) -> Sealed a -> b
unseal f x = f (seriouslyUnsafeUnseal x)
unsealM :: Monad m => m (Sealed a) -> (FORALL(x) a C(x) -> m b) -> m b
unsealM m1 m2 = do sx <- m1
unseal m2 sx
liftSM :: Monad m => (FORALL(x) a C(x) -> b) -> m (Sealed a) -> m b
liftSM f m = do sx <- m
return (unseal f sx)
mapSeal :: (FORALL(x) a C(x ) -> b C(x )) -> Sealed a -> Sealed b
mapSeal f = unseal (seal . f)
mapFlipped :: (FORALL(x) a C(x y) -> b C(x z)) -> FlippedSeal a C(y) -> FlippedSeal b C(z)
mapFlipped f (FlippedSeal x) = FlippedSeal (f x)
seriouslyUnsafeUnseal2 :: Sealed2 a -> a C(() ())
seriouslyUnsafeUnseal2 (Sealed2 a) = unsafeCoerce# a
unseal2 :: (FORALL(x y) a C(x y ) -> b) -> Sealed2 a -> b
unseal2 f a = f (seriouslyUnsafeUnseal2 a)
mapSeal2 :: (FORALL(x y) a C(x y ) -> b C(x y )) -> Sealed2 a -> Sealed2 b
mapSeal2 f = unseal2 (seal2 . f)
unsealFlipped :: (FORALL(x y) a C(x y) -> b) -> FlippedSeal a C(z) -> b
unsealFlipped f (FlippedSeal a) = f a
instance Show1 a => Show (Sealed a) where
showsPrec d (Sealed x) = showParen (d > app_prec) $ showString "Sealed " . showsPrec1 (app_prec + 1) x
instance Show2 a => Show (Sealed2 a) where
showsPrec d (Sealed2 x) = showParen (d > app_prec) $ showString "Sealed2 " . showsPrec2 (app_prec + 1) x