NAME

       CheckDigits::MXX_004 - compute check digits for VAT RN (AT)

SYNOPSIS

         use Algorithm::CheckDigits;

         $vat = CheckDigits('ustid_at');

         if ($vat->is_valid('U13585627')) {
               # do something
         }

         $cn = $vat->complete('U1358562');
         # $cn = 'U13585627'

         $cd = $vat->checkdigit('U13585627');
         # $cd = '7'

         $bn = $vat->basenumber('U13585627');
         # $bn = 'U1358562'

DESCRIPTION

   ALGORITHM
       1.  Beginning right all numbers before the check digit are weighted alternatively 1 and 2.

       2.  The total of the digits of all products is computed and then subtracted from 96.

       3.  The check digit is the sum of step 3 taken modulo 10.

   METHODS
       is_valid($number)
           Returns true only if $number consists solely of numbers and the last 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 concatenated to the end of $number.

           Returns the complete number with check digit or '' if $number does not consist solely
           of digits and spaces.

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

           Return '' otherwise.

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

           Return '' otherwise.

   EXPORT
       None by default.

AUTHOR

       Mathias Weidner, <mathias@weidner.in-bad-schmiedeberg.de>

SEE ALSO

       perl, CheckDigits, www.pruefziffernberechnung.de.