NAME

       CheckDigits::MBase_003 - compute check digits for SICI (Serial Item and Contribution
       Identifier)

SYNOPSIS

         use Algorithm::CheckDigits;

         $sici = CheckDigits('sici');

         if ($sici->is_valid('0784-8679(20040308)6:<138>2.0.TX;2-H')) {
               # do something
         }

         $cn = $sici->complete('0784-8679(20040308)6:<138>2.0.TX;2-');
         # $cn = '0784-8679(20040308)6:<138>2.0.TX;2-H'

         $cd = $sici->checkdigit('0784-8679(20040308)6:<138>2.0.TX;2-H');
         # $cd = 'H'

         $bn = $sici->basenumber('0784-8679(20040308)6:<138>2.0.TX;2-H');
         # $bn = '0784-8679(20040308)6:<138>2.0.TX;2-';

DESCRIPTION

   ALGORITHM
       0   In the string describing the number all letters (A-Z) are replaced with numbers 10-35
           accordingly. All other non-numbers are replaced by 36.

       1   Beginning right the numbers at all odd positions are added.

       2   The sum from step 1 is multiplied by 3.

       3   Beginning right the numbers at all even positions are added.

       4   The sums from step 2 and 3 are added.

       5   The sum from step 4 is taken modulo 37.

       6   The checksum is 37 minus the sum from step 5 where numbers from 10 to 35 are
           represented by 'A' to 'Z' accordingly and 36 is represented by '#'.

   METHODS
       is_valid($number)
           Returns true only if the last letter is a valid check letter according to the
           algorithm given above.

           Returns false otherwise,

       complete($number)
           The check letter for $number is computed and appended the end of $number.

           Returns the complete number with check letter or ''.

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

           Return '' otherwise.

       checkdigit($number)
           Returns the check letter of $number if $number has valid check digits.

           Return '' otherwise.

   EXPORT
       None by default.

AUTHOR

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

SEE ALSO

       perl, CheckDigits, www.pruefziffernberechnung.de,
       http://sunsite.berkeley.edu/SICI/sici.pdf