NAME

CheckDigits::M11_001 - compute check digits for ISBN, ISSN, VAT RN (PT), HKID (HK), Wagon number (BR), NHS (GB), VAT (SL)

SYNOPSIS

  use Algorithm::CheckDigits;
  $isbn = CheckDigits('isbn');
  if ($isbn->is_valid('3-88229-192-3')) {
        # do something
  }
  $cn = $isbn->complete('3-88229-192-');
  # $cn = '3-88229-192-3'
  $cd = $isbn->checkdigit('3-88229-192-3');
  # $cd = '3'
  $bn = $isbn->basenumber('3-88229-192-3');
  # $bn = '3-88229-192-'

DESCRIPTION

ALGORITHM

1.: The sequence of digits is processed right to left. Every digit is multiplied with their position in the sequence (i.e. the digit left to the check digit has the weight 2 then 3 etc.).
With a Hongkong ID (hkid) the leftmost char is replaced with its position in the alphabet and then multiplied with 8 (its weight).
2.: The sum of all products is computed.
3.: The sum of step 2 is taken modulo 11.
4.: The checkdigit is the difference of the sum from step 3 to eleven under the following conditions:

isbn,issn: If the difference is 10, the check digit is 'X'.
If the difference is 11, the check digit is 0.
ustid_pt: If the difference is greater then 9, the check digit is '0'.
hkid: If the difference is 10, the check digit is 'A'.
If the difference is 11, the check digit is 0.
wagonnr_br: If the difference is 10, the check digit is 0.
If the difference is 11, the check digit is 1.
nhs_gb: If the difference is 10, the number would not be taken.
If the difference is 11, the check digit is 0.
vat_sl: This is a little bit unclear, don't trust on the method for this type.

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>"