How to Create an Array of Unique Random Numbers

• 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

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.

MORE INFORMATION

Step-by-Step Example

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)