NAME

       CheckDigits::M11_003 - compute check digits for PKZ (GDR)

SYNOPSIS

         use Algorithm::CheckDigits;

         $pkz = CheckDigits('pkz');

         if ($pkz->is_valid('150765400354')) {
               # do something
         }

         $cn = $pkz->complete('15076540035');
         # $cn = '150765400354'

         $cd = $pkz->checkdigit('150765400354');
         # $cd = '4'

         $bn = $pkz->basenumber('150765400354');
         # $bn = '150765400354'

DESCRIPTION

   ALGORITHM
       1.  The checkdigit is set to 0.

       2.  From right to left the digits are weighted (multiplied) with 2,4,8,5,10,9,7,3,6,1,2,4.

       3.  The products are added.

       4.  The sum of step 3 is taken modulo 11.

       5.  The value of step 4 is added to a multiple (0..9) of the weight of the checkdigit (2).

       6.  The sum of step 5 is taken modulo 11.

       7.  The checkdigit is the multiple of the weight of the checkdigit where the value of step
           6 equals 10.

       8.  If there can't be reached a value of 10 in step 6, the number cannot be taken as a
           PKZ.

       To validate a PKZ apply steps 2 to 4 to the complete number.

   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.