NAME

       CheckDigits::M11_011 - compute check digits for VAT Registration Number (NL)

SYNOPSIS

         use Algorithm::CheckDigits;

         $ustid = CheckDigits('ustid_nl');

         if ($ustid->is_valid('123456782')) {
               # do something
         }
         if ($ustid->is_valid('123456782B04')) {
               # do something
         }

         $cn = $ustid->complete('12345678');
         # $cn = '123456782'
         $cn = $ustid->complete('12345678.B04');
         # $cn = '123456782B04'

         $cd = $ustid->checkdigit('123456782');
         # $cd = '2'
         $cd = $ustid->checkdigit('123456782B04');
         # $cd = '2'

         $bn = $ustid->basenumber('123456782');
         # $bn = '12345678';
         $bn = $ustid->basenumber('123456782B04');
         # $bn = '12345678.B04';

DESCRIPTION

       This VATRN has 12 "digits", the third last must be a B, the fourth last is the checkdigit.
       I don't know anything about the meaning of the last two digits.

       You may use the whole VATRN or only the first eight digits to compute the checkdigit with
       this module.

   ALGORITHM
       1.  Beginning right with the digit before the checkdigit all digits are weighted with
           their position. I.e. the digit before the checkdigit is multiplied with 2, the next
           with 3 and so on.

       2.  The weighted digits are added.

       3.  The sum from step 2 is taken modulo 11.

       4.  If the sum from step 3 is 10, the number is discarded.

   METHODS
       is_valid($number)
           Returns true only if the first eight positions of $number consist solely of digits
           (maybe followed by 'B' and to further digits) and the eighth digit is a valid check
           digit according to the algorithm given above.

           Returns false otherwise,

       complete($number)
           The check digit for $number is computed and inserted at position eight of $number.

           Returns the complete number with check digit or '' if $number does not consist solely
           of digits a dot and maybe 'B' at the ninth position.

       basenumber($number)
           Returns the basenumber of $number if $number has a valid check digit.

           Return '' otherwise.

       checkdigit($number)
           Returns the check digits of $number if $number has valid check digits.

           Return '' otherwise.

   EXPORT
       None by default.

SEE ALSO

       perl, CheckDigits, www.pruefziffernberechnung.de,

AUTHOR

       Mathias Weidner, "<mamawe@cpan.org>"

COPYRIGHT AND LICENSE

       Copyright 2004-2020 by Mathias Weidner

       This library is free software; you can redistribute it and/or modify it under the same
       terms as Perl itself.