haskus-system- Haskus system programming framework

Safe HaskellNone



Union (as in C)

Unions are storable and can contain any storable data.

Use fromUnion to read a alternative:


getUnion :: IO (Union '[Word16 Word32 Word64])
getUnion = ...

test = do
   u <- getUnion

   -- to get one of the member
   let v = fromUnion u :: Word16
   let v = fromUnion u :: Word32
   let v = fromUnion u :: Word64

   -- This won't compile (Word8 is not a member of the union)
   let v = fromUnion u :: Word8

Use toUnion to create a new union: @

let u2 :: Union '[Word32, Vector 4 Word8] u2 = toUnion (0x12345678 :: Word32) @



data Union x Source #

An union

We use a list of types as a parameter.

The union is just a pointer to a buffer containing the value(s). The size of the buffer is implicitly known from the types in the list.


Show (Union x) Source # 


showsPrec :: Int -> Union x -> ShowS #

show :: Union x -> String #

showList :: [Union x] -> ShowS #

(HFoldr' FoldSizeOf Word l Word, HFoldr' FoldAlignment Word l Word) => Storable (Union l) Source # 


peekIO :: Ptr (Union l) -> IO (Union l) Source #

pokeIO :: Ptr (Union l) -> Union l -> IO () Source #

alignment :: Union l -> Word Source #

sizeOf :: Union l -> Word Source #

(KnownNat (Max (MapSizeOf fs)), KnownNat (Max (MapAlignment fs))) => StaticStorable (Union fs) Source # 

Associated Types

type SizeOf (Union fs) :: Nat Source #

type Alignment (Union fs) :: Nat Source #


staticPeekIO :: Ptr (Union fs) -> IO (Union fs) Source #

staticPokeIO :: Ptr (Union fs) -> Union fs -> IO () Source #

type SizeOf (Union fs) Source # 
type SizeOf (Union fs)
type Alignment (Union fs) Source # 
type Alignment (Union fs)

fromUnion :: (Storable a, IsMember a l ~ True) => Union l -> a Source #

Retrieve a union member from its type

toUnion :: forall a l. (Storable (Union l), Storable a, IsMember a l ~ True) => a -> Union l Source #

Create a new union from one of the union types

toUnionZero :: forall a l. (Storable (Union l), Storable a, IsMember a l ~ True) => a -> Union l Source #

Like toUnion but set the remaining bytes to 0