NAME

       CheckDigits::MXX_001 - compute check digits for german Personalausweis (pa_de) or ABA
       routing numbers (aba_rn)

SYNOPSIS

         use Algorithm::CheckDigits;

         $pa = CheckDigits('pa_de');

         if ($pa->is_valid('2406055684D<<6810203<0705109<6')) {
               # do something
         }

         if ($pa->is_valid('2406055684') {
               # do_something
         }

         $cn = $pa->complete('240605568_D<<681020_<070510_<_');
         # $cn = '2406055684D<<6810203<0705109<6'

         $cd = $pa->checkdigit('2406055684D<<6810203<0705109<6');
         # $cd = '6'

         $bn = $pa->basenumber('2406055684D<<6810203<0705109<6');
         # $bn = '240605568_D<<681020_<070510_<_'

         $aba = CheckDigits('aba_rn');
         if ($aba->is_valid('789456124')) {
              # do something
         }

DESCRIPTION

   ALGORITHM
       1.  Beginning left all digits are weighted with 7,3,1,7,3,1,... for pa_de or
           3,7,1,3,7,1,3,7,1 for aba_rn.

       2.  The sum of those products is computed.

       3.  For pa_de the checksum is the last digit of the sum from step 2 (modulo 10).

           For aba_rn the checksum is the difference of the sum from step 2 to the next multiple
           of 10.

       4.  For the german Personalausweis step 1 to 3 is performed for every part of the number
           and for all 3 parts including the particular checkdigit to compute the total checksum.

           If the number solely consists of digits, the checksum is just computed once according
           to algorithm given above.

   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, "<mamawe@cpan.org>"

THANKS

       Aaron W. West pointed me to a fault in the computing of the check digit. Jim Hickstein
       made me aware of the ABA routing numbers.

SEE ALSO

       perl, CheckDigits, www.pruefziffernberechnung.de,
       http://answers.google.com/answers/threadview/id/43619.html,
       http://www.brainjar.com/js/validation/