Control.Concurrent.Unique

An abstract interface to a concurrent unique symbol generator.

Unlike Data.Unique from base the values are not a member of Ord. However, there is no global bottleneck.

Documentation

data Unique

Unique identifiers are created by creating heap objects in kind # that can be compared for value equality and then hashing them using their initial allocation address.

>>> x <- newUnique
>>> y <- newUnique
>>> z <- newUnique

>>> [x == x, y == y, z == z]
[True,True,True]

>>> [x == y, y == z, z == x]
[False,False,False]

The hashes could be same, in theory, but in practice they are different as well.

>>> [ hash x == hash x, hash y == hash y, hash z == hash z]
[True,True,True]

>>> [ hash x == hash y, hash y == hash z, hash z == hash x]
[False,False,False]

Instances

Eq Unique

Defined in Control.Concurrent.Unique

Methods

(==) :: Unique -> Unique -> Bool

(/=) :: Unique -> Unique -> Bool

Hashable Unique

Defined in Control.Concurrent.Unique

Methods

hashWithSalt :: Int -> Unique -> Int

hash :: Unique -> Int

newUnique :: IO Unique

Allocate a new Unique value. The value returned will not compare equal to any other value of type Unique returned by previous calls to newUnique. There is no limit on the number of times newUnique may be called.