# Verhoeff ( numericString ; index ; checkSum )

Returns the Verhoeff dihedral check digit of numericString. Use this function to verify a numeric string protected by a Verhoeff check digit, or to generate the correct Verhoeff check digit for a given numeric string.

Sample input:
Verhoeff ( "1428570" ; 0 ; 0 )

Middle ( "0432156789" ; Verhoeff ( "142857" & "0" ; 0 ; 0 ) + 1 ; 1 )
Sample output:
0

0

Function definition: (Copy & paste into FileMaker's Edit Custom Function window)

Returns the Verhoeff dihedral check digit of numericString. Use this function to verify a numeric string protected by a Verhoeff check digit, or to generate the correct Verhoeff check digit for a given numeric string.

http://en.wikipedia.org/wiki/Verhoeff_algorithm

EXAMPLES OF CALLING THE FUNCTION

1. To extract the check digit from a string in Input field:

Verhoeff ( Input ; 0 ; 0 )

A result of zero (0) indicates a valid entry; any other result indicates a data entry error.

2. To validate an entry in Input field:

not Verhoeff ( Input ; 0 ; 0 )

3. To generate a check digit for a string in Input field:

Middle ( "0432156789" ; Verhoeff ( Input & "0" ; 0 ; 0 ) + 1 ; 1 )

4. To append a check digit to a string in Input field:

Input & Middle ( "0432156789" ; Verhoeff ( Input & "0" ; 0 ; 0 ) + 1 ; 1 )