base-4.20.0.0: Core data structures and operations
Copyright(c) The University of Glasgow 2001
LicenseBSD-style (see the file libraries/base/LICENSE)
Maintainerlibraries@haskell.org
Stabilitystable
Portabilitynon-portable
Safe HaskellSafe
LanguageHaskell2010

Data.Unique

Description

An abstract interface to a unique symbol generator.

Synopsis

Unique objects

data Unique Source #

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

Instances details
Eq Unique 
Instance details

Defined in GHC.Internal.Data.Unique

Ord Unique 
Instance details

Defined in GHC.Internal.Data.Unique

newUnique :: IO Unique Source #

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 Source #

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.