SYNOPSIS

use Algorithm::CheckDigits;
$ustid = CheckDigits('ustid_nl');
if ($ustid->is_valid('123456782')) {
# do something
}
if ($ustid->is_valid('123456782B04')) {
# do something
}
$cn = $ustid->complete('12345678');
# $cn = '123456782'
$cn = $ustid->complete('12345678.B04');
# $cn = '123456782B04'
$cd = $ustid->checkdigit('123456782');
# $cd = '2'
$cd = $ustid->checkdigit('123456782B04');
# $cd = '2'
$bn = $ustid->basenumber('123456782');
# $bn = '12345678';
$bn = $ustid->basenumber('123456782B04');
# $bn = '12345678.B04';

DESCRIPTION

This VATRN has 12 ``digits'', the third last must be a B, the fourth last is the checkdigit. I don't know anything about the meaning of the last two digits.

You may use the whole VATRN or only the first eight digits to compute the checkdigit with this module.

ALGORITHM

1.

Beginning right with the digit before the checkdigit all digits are weighted with their position. I.e. the digit before the checkdigit is multiplied with 2, the next with 3 and so on.

2.

The weighted digits are added.

3.

The sum from step 2 is taken modulo 11.

4.

If the sum from step 3 is 10, the number is discarded.

METHODS

is_valid($number)

Returns true only if $number consists solely of numbers and hyphens and the two digits in the middle are valid check digits according to the algorithm given above.

Returns false otherwise,

complete($number)

The check digit for $number is computed and inserted into the middle of $number.

Returns the complete number with check digit or '' if $number does not consist solely of digits, hyphens and spaces.

basenumber($number)

Returns the basenumber of $number if $number has a valid check digit.

Return '' otherwise.

checkdigit($number)

Returns the check digits of $number if $number has valid check digits.

Return '' otherwise.

EXPORT

None by default.

AUTHOR

Mathias Weidner, <[email protected]>

COPYRIGHT AND LICENSE

Copyright 2004,2005 by Mathias Weidner

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.