Q192764: HOWTO: Provide Inverse AT() Functionality

Article: Q192764
Product(s): Microsoft FoxPro
Version(s): MACINTOSH:2.6a,3.0b; MS-DOS:2.0,2.5,2.5a,2.5b,2.6,2.6a; UNIX:2.6; WINDOWS:2.6a,3.0,3.0b
Operating System(s): 
Keyword(s): 
Last Modified: 11-DEC-1999

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b, 5.0, 5.0a, 6.0 
- Microsoft Visual FoxPro for Macintosh, version 3.0b 
- Microsoft FoxPro for Windows, version 2.6a 
- Microsoft FoxPro for UNIX, version 2.6 
- Microsoft FoxPro for MS-DOS, versions 2.0, 2.5, 2.5a, 2.5b, 2.6, 2.6a 
- Microsoft FoxPro for Macintosh, version 2.6a 
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SUMMARY
=======

The AT(), RAT() and equivalent functions can be used to return the beginning
numeric position of the first occurrence of a character expression within
another character expression. However, FoxPro does not provide a function to
find the first occurrence of a character that is not the character that was
passed as a parameter. In other words, suppose that you have a string "AAAAB"
and you wish to find the first occurrence of a character that is not "A". This
article demonstrates how to provide this functionality.

MORE INFORMATION
================

Save the following code to a program file and run the program. The NotAt()
function returns the second occurrence of a character that is not a "0" (zero).
Here is the sample code:

     *-- Code begins here.
     CLEAR
     ? NotAt("0", "0x00CCAF77A", 2)

     *-----------------------------------------------------------------
     *- Function:    NotAt
     *- Summary:     From within a passed string, finds the first
     *-              occurence of a character that is not the character
     *-              specified.  In other words, this function works
     *-              opposite of the manner that AT() does.
     *- Parameters:  lsNotString -    What we don't want.  The function
     *-                               finds the first character that is
     *-                               not lsNotString.
     *-              lsSearchString - The string in which to search.
     *-              liOccurence -    Indicates that NotAt should find
     *-                               the liOccurence of a character
     *-                               that is not lsNotString.
     *-----------------------------------------------------------------
     FUNCTION NotAt
     PARAMETERS lsNotString, lsSearchString, liOccurrence

     llFound       = .F.  && Flag indicates if we've found a character that
                          && is NOT lsNotString.
     llEndOfString = .F.  && Flag to indicate that we've reached the end
                          && of the string.
     lnCounter     = 0    && Tracks position during the search.
     lnLength      = LEN(lsSearchString)
     liOccurCount  = 0    && Tracks how many occurrences have been found.

     *-- Loop until the desired character is found or the end of
     *-- the string is reached.
     DO WHILE NOT llFound AND NOT llEndofString
        lnCounter = lnCounter + 1
        lsCompare = SUBSTR(lsSearchString, lnCounter, 1)
        IF lsCompare <> lsNotString
           liOccurCount = liOccurCount + 1

           *-- Have we found the occurrence we want?
           IF liOccurCount = liOccurrence
              llFound = .T.
           ENDIF
        ENDIF
        IF lnCounter = lnLength
           llEndOfString = .T.
        ENDIF
     ENDDO
     RETURN lnCounter
     *-- Code ends here.

REFERENCES
==========

(c) Microsoft Corporation 1998, All Rights Reserved.
Contributions by Mike A. Stewart, Microsoft Corporation


Additional query words: kbVFp300b kbVFp500a kbVFp500 kbVFp600 kbXBase

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Keywords          :  
Technology        : kbHWMAC kbOSMAC kbVFPsearch kbAudDeveloper kbFoxproSearch kbZNotKeyword3 kbFoxPro260aMac kbFoxPro200DOS kbFoxPro250DOS kbFoxPro250aDOS kbFoxPro250bDOS kbFoxPro260DOS kbFoxPro260aDOS kbFoxPro260UNIX kbFoxPro260a kbVFP300bMac kbVFP300 kbVFP300b kbVFP500 kbVFP600 kbVFP500a
Version           : MACINTOSH:2.6a,3.0b; MS-DOS:2.0,2.5,2.5a,2.5b,2.6,2.6a; UNIX:2.6; WINDOWS:2.6a,3.0,3.0b,5.0,5.0a,6.0
Issue type        : kbhowto

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