NAME

       CheckDigits::M10_003 - compute check digits for ISMN

SYNOPSIS

         use Algorithm::CheckDigits;

         $ismn = CheckDigits('ismn');

         if ($ismn->is_valid('M-345-24680-5')) {
               # do something
         }

         $cn = $ismn->complete('M-345-24680');
         # $cn = 'M-345-24680-5'

         $cd = $ismn->checkdigit('M-345-24680-5');
         # $cd = '5'

         $bn = $ismn->basenumber('M-345-24680-5');
         # $bn = 'M-345-24680'

DESCRIPTION

   ALGORITHM
       1.  The 'M' as the first number gets the value 3.  Beginning left all numbers are weighted
           alternatively 3 and 1.

       2.  The sum of all products is computed.

       3.  The sum of step 3 ist taken modulo 10.

       4.  The check digit is the difference between 10 and the number from 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, "<mamawe@cpan.org>"

SEE ALSO

       perl, CheckDigits, www.pruefziffernberechnung.de.