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, <mathias@weidner.in-bad-schmiedeberg.de>

SEE ALSO

perl, CheckDigits, www.pruefziffernberechnung.de.