NAME

CheckDigits::M11_008 - compute check digits for VAT Registration Number (DK)

SYNOPSIS

  use Algorithm::CheckDigits;

  $ustid = CheckDigits('ustid_dk');

  if ($ustid->is_valid('13585628')) {
        # do something
  }

  $cn = $ustid->complete('1358562');
  # $cn = '13585628'

  $cd = $ustid->checkdigit('13585628');
  # $cd = '8'

  $bn = $ustid->basenumber('13585628');
  # $bn = '1358562';


=head1 DESCRIPTION

ALGORITHM

Beginning left every digit is weighted with 2, 7, 6, 5, 4, 3, 2, 1
The weighted digits are added.
The sum from step 2 is taken modulo 11.
The number is valid if the sum from step 3 is zero (0).

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 '' if $number is valid.

Return undef otherwise.

EXPORT

None by default.

AUTHOR