# NAME

CheckDigits::M11_003 - 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'
``````

# DESCRIPTION

## 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.

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, `<mamawe@cpan.org>`