"

======================================================================

|

| Copyright (C) 1988, 1989 Free Software Foundation, Inc.

| Written by Steve Byrne.

|

| This file is part of GNU Smalltalk.

|

| GNU Smalltalk is free software; you can redistribute it and/or modify it

| under the terms of the GNU General Public License as published by the Free

| Software Foundation; either version 1, or (at your option) any later version.

| 

| GNU Smalltalk is distributed in the hope that it will be useful, but WITHOUT

| ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

| FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more

| details.

| 

| You should have received a copy of the GNU General Public License along with

| GNU Smalltalk; see the file LICENSE.  If not, write to the Free Software

| Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  

|

======================================================================

see notice in (Random>>documentation)

"

"{ Package: 'stx:libbasic2' }"

"{ NameSpace: Smalltalk }"

Random subclass:#RandomGNUSmalltalk

	instanceVariableNames:'increment multiplier modulus'

	classVariableNames:'SharedGenerator'

	poolDictionaries:''

	category:'Magnitude-Numbers-Random'

!

!RandomGNUSmalltalk class methodsFor:'documentation'!

copyright

"

======================================================================

|

| Copyright (C) 1988, 1989 Free Software Foundation, Inc.

| Written by Steve Byrne.

|

| This file is part of GNU Smalltalk.

|

| GNU Smalltalk is free software; you can redistribute it and/or modify it

| under the terms of the GNU General Public License as published by the Free

| Software Foundation; either version 1, or (at your option) any later version.

| 

| GNU Smalltalk is distributed in the hope that it will be useful, but WITHOUT

| ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

| FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more

| details.

| 

| You should have received a copy of the GNU General Public License along with

| GNU Smalltalk; see the file LICENSE.  If not, write to the Free Software

| Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  

|

======================================================================

see notice in (Random>>documentation)

"

!

documentation

"

    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.

    [author:]

        Steve Byrne

        Claus Gittinger

    [see also:]

        http://www0.cs.ucl.ac.uk/staff/d.jones/GoodPracticeRNG.pdf

        RandomTT800      - a new random generator

        RandomParkMiller - another new random generator

"

!

examples

"

                                                                        [exBegin]

    |rnd|

    rnd := RandomGNUSmalltalk new.

    10 timesRepeat:[

        Transcript showCR:(rnd next)

    ]

                                                                        [exEnd]

    rolling a dice:

                                                                        [exBegin]

    |rnd|

    rnd := RandomGNUSmalltalk new.

    10 timesRepeat:[

        Transcript showCR:(rnd nextIntegerBetween:1 and:6)

    ]

                                                                        [exEnd]

"

! !

!RandomGNUSmalltalk methodsFor:'accessing-reading'!

maxInteger

    ^ modulus

!

next

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

    self step.

    ^ seed / modulus asFloat

    "

     |r|

     r := Random new.

     Transcript showCR:r next.

     Transcript showCR:r next.

     Transcript showCR:r next.

     Transcript showCR:r next.

    "

    "Modified: 1.4.1997 / 22:44:46 / cg"

!

nextBoolean

    "return true or false by random"

    self step.

    ^ seed < (modulus // 2)

    "

    |r|

     r := Random new.

     Transcript showCR:r nextBoolean.

     Transcript showCR:r nextBoolean.

     Transcript showCR:r nextBoolean.

     Transcript showCR:r nextBoolean.

    "

    "

     |r bag|

     r := Random new.

     bag := Bag new.

     1000000 timesRepeat:[

         bag add:(r nextBoolean).

     ].

     Transcript showCR:bag contents

    "

    "Modified: / 22-10-2008 / 15:17:57 / cg"

!

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!!"

    self step.

    ^ seed

    "

     |r|

     r := Random new.

     Transcript showCR:r nextInteger.

     Transcript showCR:r nextInteger.

     Transcript showCR:r nextInteger.

     Transcript showCR:r nextInteger.

    "

    "Modified: 1.4.1997 / 22:42:53 / cg"

! !

!RandomGNUSmalltalk methodsFor:'private'!

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!!"

    modulus := 244944 " 244957 " .

    multiplier := 1597.

    increment := 51749.

    seed := seedValue \\ modulus.

    self step.

    "Modified: / 12-11-1999 / 17:50:52 / stefan"

    "Created: / 26-05-2007 / 21:25:10 / cg"

!

step

    "compute the next random integer"

    seed := (seed * multiplier + increment) \\ modulus

    "Created: 1.4.1997 / 22:40:45 / cg"

    "Modified: 1.4.1997 / 22:43:01 / cg"

! !

!RandomGNUSmalltalk class methodsFor:'documentation'!

version

    ^ '$Header$'

!

version_CVS

    ^ '$Header$'

! !