Data.HashCons.ConstRef

Read-only references with pointer equality.

Documentation

data ConstRef a

A read-only reference.

A ConstRef is similar to an IORef in that it has its own identity.

do a <- newConstRef ()
   b <- newConstRef ()
   return $ a == b
     -- False

However, unlike most types of reference, it is immutable and its value is set at construction time. This is the reason why readConstRef does not need to return an IO value.

Instances

Eq (ConstRef a)

Pointer equality

Methods

(==) :: ConstRef a -> ConstRef a -> Bool

(/=) :: ConstRef a -> ConstRef a -> Bool

MkWeak (ConstRef a)

Methods

mkWeak :: ConstRef a -> v -> Maybe Finalizer -> IO (Weak v)

mkWeakPtr :: ConstRef a -> Maybe Finalizer -> IO (Weak (ConstRef a))

addFinalizer :: ConstRef a -> Finalizer -> IO ()

newConstRef :: a -> IO (ConstRef a)

Make a new ConstRef.

readConstRef :: ConstRef a -> a

Read the value of a ConstRef.