StableName

Documentation

data StableName a

An abstract name for an object, that supports equality and hashing.

Stable names have the following property:

• If sn1 :: StableName and sn2 :: StableName and sn1 == sn2 then sn1 and sn2 were created by calls to makeStableName on the same object.

The reverse is not necessarily true: if two stable names are not equal, then the objects they name may still be equal. Note in particular that makeStableName may return a different StableName after an object is evaluated.

Stable Names are similar to Stable Pointers (Foreign.StablePtr), but differ in the following ways:

• There is no freeStableName operation, unlike Foreign.StablePtrs. Stable names are reclaimed by the runtime system when they are no longer needed.
• There is no deRefStableName operation. You can't get back from a stable name to the original Haskell object. The reason for this is that the existence of a stable name for an object does not guarantee the existence of the object itself; it can still be garbage collected.

Instances

NFData1 StableName

Since: deepseq-1.4.3.0

Defined in Control.DeepSeq

Methods

liftRnf :: (a -> ()) -> StableName a -> ()

Eq (StableName a)

Since: base-2.1

Defined in System.Mem.StableName

Methods

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

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

Hashable (StableName a)

Defined in Data.Hashable.Class

Methods

hashWithSalt :: Int -> StableName a -> Int

hash :: StableName a -> Int

NFData (StableName a)

Since: deepseq-1.4.0.0

Defined in Control.DeepSeq

Methods

rnf :: StableName a -> ()

makeStableName :: a -> IO (StableName a)

Makes a StableName for an arbitrary object. The object passed as the first argument is not evaluated by makeStableName.

hashStableName :: StableName a -> Int

Convert a StableName to an Int. The Int returned is not necessarily unique; several StableNames may map to the same Int (in practice however, the chances of this are small, so the result of hashStableName makes a good hash key).

eqStableName :: StableName a -> StableName b -> Bool

Equality on StableName that does not require that the types of the arguments match.

Since: base-4.7.0.0