NAME

       CheckDigits::MBase_001 - compute check digits for UPC (US)

SYNOPSIS

         use Algorithm::CheckDigits;

         $rv = CheckDigits('upc');

         if ($rv->is_valid('012345678905')) {
               # do something
         }

         $cn = $rv->complete('01234567890');
         # $cn = '012345678905'

         $cd = $rv->checkdigit('012345678905');
         # $cd = '5'

         $bn = $rv->basenumber('012345678905');
         # $bn = '01234567890'

DESCRIPTION

   ALGORITHM
       1.  Add all digits in odd-numbered positions.

       2.  Multiply the sum from step 1 with 3.

       3.  Add all digits in even-numbered positions.

       4.  Add the product from step 2 and the sum from step 3.

       5.  If the sum from step 4 is 0 modulo 10, the check digit is 0. Else the check digit is
           10 minus the sum from step 4 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>

THANKS

       Aaron W. West pointed me to a fault in the computing of the check digit.

SEE ALSO

       perl, CheckDigits, www.pruefziffernberechnung.de,
       www.export911.com/e911/coding/upcChar.htm, www.adams1.com/pub/russadam/upccode.html,
       http://www.upcdatabase.com.