Data.Unique

An abstract interface to a unique symbol generator.

Unique objects

data Unique

An abstract unique object. Objects of type Unique may be compared for equality and ordering and hashed into Int.

>>> :{
do x <- newUnique
   print (x == x)
   y <- newUnique
   print (x == y)
:}
True
False

Instances

Eq Unique

Defined in Data.Unique

Methods

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

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

Ord Unique

Defined in Data.Unique

Methods

compare :: Unique -> Unique -> Ordering

(<) :: Unique -> Unique -> Bool

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

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

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

max :: Unique -> Unique -> Unique

min :: Unique -> Unique -> Unique

newUnique :: IO Unique

Creates a new object of type Unique. 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.

hashUnique :: Unique -> Int

Hashes a Unique into an Int. Two Uniques may hash to the same value, although in practice this is unlikely. The Int returned makes a good hash key.