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Class: RandomGNUSmalltalk


Inheritance:

   Object
   |
   +--Stream
      |
      +--Random
         |
         +--RandomGNUSmalltalk

Package:
stx:libbasic2
Category:
Magnitude-Numbers-Random
Version:
rev: 1.2 date: 2018/03/02 16:08:05
user: cg
file: RandomGNUSmalltalk.st directory: libbasic2
module: stx stc-classLibrary: libbasic2
Author:
Steve Byrne
Claus Gittinger

Description:


WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING
=======================================================================================
DO NOT USE THIS GENERATOR FOR CRYPTOGRAPHY OR OTHER SECURITY RELATED WORK, 
because linear congruential generators are predictable and can be broken easily!

Smalltalk/X includes a better generator named RandomGenerator, 
which uses the best available generator of the system 
(either OS-random, /dev/random or as a less dangerous fallback, an RC4-based random generator).
Please use that one.
=======================================================================================

A simple random numbers - thanks to Steves GNU Smalltalk

This implements a linear congruential maximum period random number generator
which passes the spectral test for randomness for dimensions 2 3 4 5 6.

Notice: although being included here,
        this file is NOT covered by the ST/X license, but by
        the FSF copyLeft (see copyright method).

        You can redistribute it under the terms stated there ...
        Also, the price you pay for ST/X does not include a charge for
        this file - it has to be considered as a separate piece of
        software, which can be copied and given away without any 
        restriction from my (CG) side.


Related information:

    http://www0.cs.ucl.ac.uk/staff/d.jones/GoodPracticeRNG.pdf
    RandomTT800
    -
    a
    new
    random
    generator
    RandomParkMiller
    -
    another
    new
    random
    generator

Instance protocol:

accessing-reading
o  maxInteger

o  next
return the next random number in the range ]0..1[

o  nextBoolean
return true or false by random

o  nextInteger
return the next integral random number,
in the range 0 .. modulus (which is less than 16r3FFFFFFF).
From Sedgewick's 'Algorithms', based on Lehmer's method.

Take care, this returns an even number after each odd number!

private
o  setSeed: seedValue
set the initial seed and intialite the PRNG parameters.
These numbers implement a maximum period generator which passes
the spectral test for randomness for dimensions 2 3 4 5 6 and
the product does not overflow 2 raisedTo:29.

These numbers are carefully choosen, so don't change them,
unless you know what you are doing!

o  step
compute the next random integer


Examples:


    |rnd|

    rnd := RandomGNUSmalltalk new.
    10 timesRepeat:[
        Transcript showCR:(rnd next)
    ]
rolling a dice:
    |rnd|

    rnd := RandomGNUSmalltalk new.
    10 timesRepeat:[
        Transcript showCR:(rnd nextIntegerBetween:1 and:6)
    ]


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