Copyright	(c) The University of Glasgow 2001
License	BSD-style (see the file libraries/base/LICENSE)
Maintainer	libraries@haskell.org
Stability	stable
Portability	non-portable
Safe Haskell	Safe
Language	Haskell2010

Data.Unique

Contents

Unique objects

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 Methods (==) :: Unique -> Unique -> Bool Source # (/=) :: Unique -> Unique -> Bool Source #
Ord Unique
Instance details Defined in GHC.Internal.Data.Unique Methods compare :: Unique -> Unique -> Ordering Source # (<) :: Unique -> Unique -> Bool Source # (<=) :: Unique -> Unique -> Bool Source # (>) :: Unique -> Unique -> Bool Source # (>=) :: Unique -> Unique -> Bool Source # max :: Unique -> Unique -> Unique Source # min :: Unique -> Unique -> Unique Source #

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.