NAME

CheckDigits::M11_013 - compute check digits for VAT Registration Number (GR)

SYNOPSIS

  use Algorithm::CheckDigits;

  $ustid = CheckDigits('ustid_gr');

  if ($ustid->is_valid('123456783')) {
	# do something
  }

  $cn = $ustid->complete('12345678');
  # $cn = '123456783'

  $cd = $ustid->checkdigit('123456783');
  # $cd = '3'

  $bn = $ustid->basenumber('123456783');
  # $bn = '12345678';
  

DESCRIPTION

ALGORITHM

1. Beginning right with the digit before the checkdigit all digits are weighted with 2 ** position. I. e. the last digit is multiplied with 2, the next with 4, then 8 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 greater than 9, the check sum is 0 else it is the sum itself.

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

SEE ALSO

perl, CheckDigits, www.pruefziffernberechnung.de,