Q136420: How to Create an Array of Unique Random Numbers

Article: Q136420
Product(s): Microsoft FoxPro
Version(s): MACINTOSH:2.5b,2.5c,2.6a; MS-DOS:2.0,2.5,2.5a,2.5b,2.6,2.6a; UNIX:2.6; WINDOWS:2.5,2.5a
Operating System(s): 
Keyword(s): 
Last Modified: 15-FEB-2000

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, version 3.0 
- Microsoft FoxPro for MS-DOS, versions 2.0, 2.5, 2.5a, 2.5b, 2.6, 2.6a 
- Microsoft FoxPro for Windows, versions 2.5, 2.5a, 2.5b, 2.6, 2.6a 
- Microsoft FoxPro for Macintosh, versions 2.5b, 2.5c, 2.6a 
- Microsoft FoxPro for UNIX, version 2.6 
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SUMMARY
=======

The FoxPro RAND() function returns a random number between 0 and 1. This article
shows by example how to:

- Create random numbers between 5 and 10.

- Easily create an array of random numbers between any two integers.

- Make the random numbers in an array unique.

The user-defined functions (UDFs) listed in this article demonstrate how.

MORE INFORMATION
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Step-by-Step Example
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1. Create a program file called Myudf.prg that contains the following code:

     FUNCTION RANDOM
     *  Returns a random number between any 2 numbers.
     *  Syntax: =RANDOM(Lower Value, Higher Value)
     *  Example:  lnX=RANDOM(5,10)
     PARAMETER anLow,anHigh
     lnRnumber=INT((RAND()*(anHigh-anLow+1))+anLow)
     RETURN lnRnumber

     FUNCTION A_RANDOM
     *  Returns an array of random numbers between any 2 numbers.
     *  The array must already be defined
     *  Syntax:   =A_RANDOM(ArrayName,Lower Value, Upper Value)
     *  Example:  =A_RANDOM('gaMyarray',17,25)
     PARAMETER lcA_name,anLow,anHigh
     lnAlength=ALEN(&lcA_name)
     FOR lni=1 TO lnAlength
       &lcA_name(lni)=INT((RAND()*(anHigh-anLow+1))+anLow)
     ENDFOR
     RETURN &lcA_name

     FUNCTION U_RANDOM
     *  Returns an array of unique random numbers  between any 2 numbers.
     *  The array must already be defined
     *  Syntax:   =U_RANDOM(Array Name, Lower Value, Upper Value)
     *  Example:  =U_RANDOM('gaMyarray',1,10)
     PARAMETER lcA_name,anLow,anHigh
     lnAlength=ALEN(&lcA_name)
     IF lnAlength>anHigh-anLow
        lnAlength=anHigh-anLow+1
     ENDIF
     &lcA_name=.F.
     lni=1
     DO WHILE lni<=lnAlength
        lnRnumber=INT((RAND()*(anHigh-anLow+1))+anLow)
        llNextnum=.T.
        IF lnRnumber=anLow .OR. lnRnumber=anHigh
           DO CASE
           CASE lnRnumber=anLow
              lnK=1
              DO WHILE lnK>0
                 anLow=anLow+1
                 lnK=ASCAN(&lcA_name,anLow)
              ENDDO
           CASE lnRnumber=anHigh
              lnK=1
              DO WHILE lnK>0
                 anHigh=anHigh-1
                 lnK=ASCAN(&lcA_name,anHigh)
              ENDDO
           ENDCASE
        ELSE
           lnK=ASCAN(&lcA_name,lnRnumber)
           IF lnK>0
              llNextnum=.F.
           ENDIF
        ENDIF
        IF llNextnum
           &lcA_name(lni)=lnRnumber
           lni=lni+1
        ENDIF
     ENDDO

2. Save and Close Myudf.prg

3. Test the functions:

  a. To print a single random number between 5 and 10, type the following in
     the Command window:

        SET PROCEDURE TO MYUDF.PRG
        ? RANDOM(5,10)

  b. To populate an array with random numbers, type the following in the
     Command window:

        SET PROCEDURE TO MYUDF.PRG
        DIMENSION gaMyarray(10)
        =A_RANDOM('gaMyarray',1,10)

  c. If you want to populate an array with unique random numbers, type the
     following in the Command window:

        SET PROCEDURE TO MYUDF.PRG
        DIMENSION gaMyarray(10)
        U_Random('gaMyarray',1,10)

Additional query words: VFoxWin FoxWin FoxDos FoxUnix

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Keywords          :  
Technology        : kbHWMAC kbOSMAC kbVFPsearch kbAudDeveloper kbFoxproSearch kbZNotKeyword3 kbFoxPro250bMac kbFoxPro260aMac kbFoxPro250cMac kbFoxPro200DOS kbFoxPro250DOS kbFoxPro250aDOS kbFoxPro250bDOS kbFoxPro260DOS kbFoxPro260aDOS kbFoxPro260UNIX kbFoxPro260 kbFoxPro250 kbFoxPro250a kbFoxPro250b kbFoxPro260a kbVFP300
Version           : MACINTOSH:2.5b,2.5c,2.6a; MS-DOS:2.0,2.5,2.5a,2.5b,2.6,2.6a; UNIX:2.6; WINDOWS:2.5,2.5a,2.5b,2.6,2.6a,3.0

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