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.