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# Manual Reference Pages  -  ALGORITHM::CHECKDIGITS::M11_003 (3)

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### 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. 3. The products are added. 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>