CheckDigits::M11_003(3) compute check digits for PKZ (GDR)

## SYNOPSIS

use Algorithm::CheckDigits;
\$pkz = CheckDigits('pkz');
if (\$pkz->is_valid('150765400354')) {
# do something
}
\$cn = \$pkz->complete('15076540035');
# \$cn = '150765400354'
\$cd = \$pkz->checkdigit('150765400354');
# \$cd = '4'
\$bn = \$pkz->basenumber('150765400354');
# \$bn = '150765400354'

## ALGORITHM

1.
The checkdigit is set to 0.
2.
From right to left the digits are weighted (multiplied) with 2,4,8,5,10,9,7,3,6,1,2,4.
3.
4.
The sum of step 3 is taken modulo 11.
5.
The value of step 4 is added to a multiple (0..9) of the weight of the checkdigit (2).
6.
The sum of step 5 is taken modulo 11.
7.
The checkdigit is the multiple of the weight of the checkdigit where the value of step 6 equals 10.
8.
If there can't be reached a value of 10 in step 6, the number cannot be taken as a PKZ.

To validate a PKZ apply steps 2 to 4 to the complete number.

## 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.

None by default.

## AUTHOR

Mathias Weidner, <[email protected]>