How to Use UDF() to Modify Default Scientific Notation Format

 Last reviewed: March 13, 1998
Article ID: Q148784
2.00 2.5x 2.60 2.60a | 2.5x 2.60 2.60a 3.00 3.00b | 2.5x 2.60a | 2.60 
MS-DOS               | WINDOWS                    | MACINTOSH  | UNIX
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The information in this article applies to:

  • Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b
  • 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 default formatting that Visual FoxPro applies to numbers requiring scientific notation does not conform to a standard that many customers expect. You can use the user-defined function (UDF) in this article to address this issue.

MORE INFORMATION

The following program is a UDF() that can process a numeric value into the standard format expected by many customers who have expressed a need for an alternative format for scientific notation: 

PARAMETERS   nPassedVal

* Program:   Num2sci.prg
*
* Purpose:   Convert FoxPro formatted numeric values requiring scientific
*            notation to the frequently requested n.nnnE+n format.
* Syntax:    NUM2SCI(nExpression)
* Arguments: nExpression is the numeric value to convert to the alternative 
*            format.
* Returns:   Character
* Important notes about minimum and maximum ranges FoxPro will address: * ------------------------------------------------------------------------- * SET DECIMALS makes no difference to any of this functionality. * FoxPro will round values beginning at the fifteenth decimal place. * Margin of error at 15 decimals or more is 3.410910030699E-15. * The maximums for the STR() function are: STR(n,25,18). * * Any value of n.nE+19 or greater will resolve to scientific notation. * * Ex: ALLTRIM(STR(1.234567890e+18,25,18)) 
*       Resolves to: "1234567890000000000.00000"
* Ex: ALLTRIM(STR(1.234567890e+19,25,18)) 
*       Resolves to: ".1234567890000004000E+20"
*
* Any value passed with n.nE-16 or lower will resolve to equal zero. * * Ex: ALLTRIM(STR(1.234567890e-15,25,18)) 
*       Resolves to: "0.000000000000001000"
* Ex: ALLTRIM(STR(1.234567890e-16,25,18)) 
*       Resolves to: "0.000000000000000000"
*
* These are limitations in FoxPro that cannot be changed. This procedure, * and therefore any data it processes, is limited to working within these * constraints. * * -------------------------------------------------------------------------

* Stage 1: Convert to character cConvStage1 = UPPER(ALLTRIM(STR(nPassedVal,25,18))) * Find initial location of decimal point nDecimalLoc = ATC(".", cConvStage1) * Find 'E' beginning notation 

nExpLoc     = RAT("E", cConvStage1)

IF nExpLoc = 0                           && No notation in resolved value.
  * Remove trailing zeros from character value
  DO WHILE SUBSTR(cConvStage1,LEN(cConvStage1),1) = '0'
    cConvStage1 = SUBSTR(cConvStage1,1,LEN(cConvStage1)-1)
  ENDDO
  cRetVal = SUBSTR(cConvStage1,1)    && Return entire number included.
decimals ELSE * Stage 2: Value deconstruction and element reformatting * Swap positions of first two characters 
  cConvStage2a = SUBSTR(cConvStage1,2,1)+"."
  * Portion between the decimal and the 'E'
  cConvStage2b = SUBSTR(cConvStage1,3,nExpLoc-3)
  * Decrement notation by 1
  cConvStage2c = "E+"+ALLTRIM(STR(VAL(SUBSTR(cConvStage1,nExpLoc+2))-1))

  * process portion between decimal and the 'E' to remove trailing Zeros
  DO WHILE SUBSTR(cConvStage2b,LEN(cConvStage2b),1) = '0'
    cConvStage2b = SUBSTR(cConvStage2b,1,LEN(cConvStage2b)-1)
  ENDDO

  * Stage 3: Value reconstruction
  cRetVal = cConvStage2a+cConvStage2b+cConvStage2c
ENDIF RETURN cRetVal

To convert the value back to numeric, use the VAL() function against the character data NUM2SCI() returned.

Additional reference words: 2.00 2.50 2.60 2.60a 3.00 3.00b FoxWin FoxMac
FoxUnix FoxDos VFoxWin
KBCategory: kbprg kbhowto kbcode
KBSubcategory: FxprgGeneral
Keywords : FxprgGeneral kbcode kbhowto kbprg
Version : 2.00 2.5x 2.60 2.60a | 2.5x 2.60
Platform : MACINTOSH MS-DOS UNIX WINDOWS

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Last reviewed: March 13, 1998
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