NAME

       CheckDigits::M11_008 - compute check digits for VAT Registration Number (DK)

SYNOPSIS

         use Algorithm::CheckDigits;

         $ustid = CheckDigits('ustid_dk');

         if ($ustid->is_valid('13585628')) {
               # do something
         }

         $cn = $ustid->complete('1358562');
         # $cn = '13585628'

         $cd = $ustid->checkdigit('13585628');
         # $cd = '8'

         $bn = $ustid->basenumber('13585628');
         # $bn = '1358562';

DESCRIPTION

   ALGORITHM
       1.  Beginning left every digit is weighted with 2, 7, 6, 5, 4, 3, 2, 1

       2.  The weighted digits are added.

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

       4.  The number is valid if the sum from step 3 is zero (0).

   METHODS
       is_valid($number)
           Returns true only if $number consists solely of numbers and the sum computed according
           to the algorithm given above is 0.

           Returns false otherwise,

       complete($number)
           Returns $number if $number is valid according to the algorithm given above.

           Return '' otherwise.

       basenumber($number)
           Returns $number if $number is valid according to the algorithm given above.

           Return '' otherwise.

       checkdigit($number)
           Returns '' if $number is valid.

           Return undef otherwise.

   EXPORT
       None by default.

AUTHOR

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

SEE ALSO

       perl, CheckDigits, www.pruefziffernberechnung.de,