"

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

|

| 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)

"

Stream subclass:#Random

	instanceVariableNames:'seed increment multiplier modulus'

	poolDictionaries:''

	category:'Magnitude-Numbers'

!

!Random 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

"

    random numbers - thanks to Steves GNU Smalltalk

    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.

    claus: the algorithm may need a rewrite for better numbers

    [author:]

        Steve Byrne

        Claus Gittinger

"

!

examples

"

                                                                        [exBegin]

    |rnd|

    rnd := Random new.

    10 timesRepeat:[

        Transcript showCR:(rnd next)

    ]

                                                                        [exEnd]

    rolling a dice:

                                                                        [exBegin]

    |rnd|

    rnd := Random new.

    10 timesRepeat:[

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

    ]

                                                                        [exEnd]

"

! !

!Random class methodsFor:'instance creation'!

new

    "return a new random generator"

    ^self basicNew setSeed

! !

!Random class methodsFor:'testing'!

chiSquareTest   

    " Chi-Squared Test - from R.Sedgewick's 1st ed. of 'Algorithms', 

            o N = number of samples

            o r  = range of random numners is [0,r)      -- condition: N >= 10r.

            o Random number generator 'passes' if chisquare value is very close to r

            o Repeat test several times, since it may be *wrong* 1 out of 10 trials."

    | aRand frequencies n range t chisquare |

    chisquare := Array new: 10.     "Collect results from 10 trails"

    1 to: 10 do: [:k |       "k = trail number"

        aRand := Random new.  "Seeded differently each time"

        range := 100.   

        n := 1000.

        frequencies := Array new: range.

        1 to: frequencies size do: [ :i | frequencies at: i put: 0 ].

        1 to: n do: [ :i |

                t := ((aRand next) * range) truncated.

                frequencies at: (t+1) put: ((frequencies at: (t + 1)) + 1) ].

        t := 0.

        1 to: range do: [ :i |

                t := t +  ((frequencies at: i) squared) ].

        chisquare at: k put: (((range * t  / n) - n) asFloat).

    ].

    ^ chisquare

    "

     Random chiSquareTest 

    "

    "

      Sedgewick claims each chisquare number should be 100 +- 20. 

      The closer to 100, the better.

    "

    "Modified: 16.4.1997 / 16:48:26 / cg"

! !

!Random methodsFor:'accessing-reading'!

next

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

    ^ self nextInteger / 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"

!

nextBetween:start and:stop

     claus: the original GNU version has a bug in returning values

     from the interval [start .. stop+1]"

    |rnd|

    rnd := self next.

    rnd := rnd * (stop asFloat - start asFloat).

    rnd := rnd + start asFloat.

    ^ rnd

    "|r|

     r := Random new.

     Transcript showCR:(r nextBetween:1 and:10).

     Transcript showCR:(r nextBetween:1 and:10).

     Transcript showCR:(r nextBetween:1 and:10).

     Transcript showCR:(r nextBetween:1 and:10).

    "

!

nextBoolean

    "return true or false by random"

    ^ self nextInteger < (modulus / 2)

    "|r|

     r := Random new.

     Transcript showCR:r nextBoolean.

     Transcript showCR:r nextBoolean.

     Transcript showCR:r nextBoolean.

     Transcript showCR:r nextBoolean.

    "

    "Modified: 1.4.1997 / 22:52:19 / cg"

!

nextInteger

    "return the next integral random number,

     in the range 0 .. 16r3FFFFFFF.

     From Sedgewick's 'Algorithms', based on Lehmer's method"

    "the times: is a kludge - times does not convert to LargeInteger on overflow"

    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"

!

nextIntegerBetween:start and:stop

    |rnd|

    rnd := self next.

    rnd := rnd * (stop asFloat - start asFloat + 1.0).

    ^ (rnd + start) truncated.

    "|r|

     r := Random new.

     Transcript showCR:(r nextIntegerBetween:1 and:10).

     Transcript showCR:(r nextIntegerBetween:1 and:10).

     Transcript showCR:(r nextIntegerBetween:1 and:10).

     Transcript showCR:(r nextIntegerBetween:1 and:10).

    "

!

nextMatchFor: aNumber

    "generate the next random, return true iff it has the same

     value as aNumber. Redefined to avoid endless reading."

    ^self next = aNumber

! !

!Random methodsFor:'blocked methods'!

contents

    "blocked from use - contents makes no sense for random generators"

    self shouldNotImplement

!

nextPut: value

    "blocked from use - it makes no sense for randoms"

    self shouldNotImplement

! !

!Random methodsFor:'private'!

setSeed

    "set the initial seed value based on the current time"

    seed := Time millisecondClockValue bitAnd:16rFFFF.

    multiplier := 2311.

    increment := 25367.

    modulus := 120050.

"/    seed := Time secondClock bitAnd: 16r3FFFFFFF

"/    multiplier := 31415821.

"/    modulus := 16r3FFFFFFF.

"/    increment := 1.

    "Modified: 1.4.1997 / 22:44:13 / cg"

!

step

    "compute the next random integer"

    "/ seed := (seed times:31415821) + 1 bitAnd: 16r3FFFFFFF.

    seed := seed * multiplier + increment \\ modulus

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

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

! !

!Random methodsFor:'testing'!

atEnd

    "instances of Random can always give more numbers"

    ^ false

!

isReadable

    ^ true

!

isWritable

    ^ false

    "Created: 1.4.1997 / 22:38:27 / cg"

! !

!Random class methodsFor:'documentation'!

version

! !