# NAME

CheckDigits::M11_002 - compute check digits for PZN (DE)

# SYNOPSIS

``````  use Algorithm::CheckDigits;

\$pzn = CheckDigits('pzn');

if (\$pzn->is_valid('4877800')) {
# do something
}

\$cn = \$pzn->complete('487780');
# \$cn = '4877800'

\$cd = \$pzn->checkdigit('4877800');
# \$cd = '0'

\$bn = \$pzn->basenumber('4877800');
# \$bn = '487780'
``````

# DESCRIPTION

## ALGORITHM

1. From left to right beginning with the first position all digits are multiplied with 2,3,4,...

3. The checkdigit ist the sum of step 2 taken modulo 11.

4. If the checkdigit is '10' the whole number is not taken as a PZN.

## 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>`