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random

Version 1.2.1.3 revision 0 uploaded by lehins.

Package meta

Synopsis
Pseudo-random number generation
Description

This package provides basic pseudo-random number generation, including the ability to split random number generators.

System.Random: pure pseudo-random number interface

In pure code, use System.Random.uniform and System.Random.uniformR from System.Random to generate pseudo-random numbers with a pure pseudo-random number generator like System.Random.StdGen.

As an example, here is how you can simulate rolls of a six-sided die using System.Random.uniformR:

>>> let roll = uniformR (1, 6)        :: RandomGen g => g -> (Word, g)

>>> let rolls = unfoldr (Just . roll) :: RandomGen g => g -> [Word]

>>> let pureGen = mkStdGen 42

>>> take 10 (rolls pureGen)           :: [Word]
[1,1,3,2,4,5,3,4,6,2]

See System.Random for more details.

System.Random.Stateful: monadic pseudo-random number interface

In monadic code, use System.Random.Stateful.uniformM and System.Random.Stateful.uniformRM from System.Random.Stateful to generate pseudo-random numbers with a monadic pseudo-random number generator, or using a monadic adapter.

As an example, here is how you can simulate rolls of a six-sided die using System.Random.Stateful.uniformRM:

>>> let rollM = uniformRM (1, 6)                 :: StatefulGen g m => g -> m Word

>>> let pureGen = mkStdGen 42

>>> runStateGen_ pureGen (replicateM 10 . rollM) :: [Word]
[1,1,3,2,4,5,3,4,6,2]

The monadic adapter System.Random.Stateful.runStateGen_ is used here to lift the pure pseudo-random number generator pureGen into the System.Random.Stateful.StatefulGen context.

The monadic interface can also be used with existing monadic pseudo-random number generators. In this example, we use the one provided in the mwc-random package:

>>> import System.Random.MWC as MWC

>>> let rollM = uniformRM (1, 6)       :: StatefulGen g m => g -> m Word

>>> monadicGen <- MWC.create

>>> replicateM 10 (rollM monadicGen) :: IO [Word]
[2,3,6,6,4,4,3,1,5,4]

See System.Random.Stateful for more details.

Author
n/a
Bug reports
https://github.com/haskell/random/issues
Category
System
Copyright
n/a
Homepage
n/a
Maintainer
core-libraries-committee@haskell.org
Package URL
n/a
Stability
n/a

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