NAME

       CheckDigits::M11_017 - compute check digits for EC-No, EINECS, ELINCS

SYNOPSIS

         use Algorithm::CheckDigits;

         $ecno = CheckDigits('ecno');

         if ($ecno->is_valid('200-236-6')) {
               # do something
         }

         $cn = $ecno->complete('200-236-');
         # $cn = '200-236-6'

         $cd = $ecno->checkdigit('200-236-6');
         # $cd = '6'

         $bn = $ecno->basenumber('200-236-6');
         # $bn = '200-236-'

DESCRIPTION

   ALGORITHM
       1.  From left to right all digits are multiplied with their position in the sequence.

       2.  The sum of all products is computed.

       3.  The sum of step 2 is taken modulo 11.

           The checkdigit is the last digit of the result.

   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, http://en.wikipedia.org/wiki/EC-No.