++ed by:

3 non-PAUSE users.

# NAME

CheckDigits::MXX_001 - compute check digits for german Personalausweis (pa_de) or ABA routing numbers (aba_rn)

# SYNOPSIS

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

\$pa = CheckDigits('pa_de');

if (\$pa->is_valid('2406055684D<<6810203<0705109<6')) {
# do something
}

if (\$pa->is_valid('2406055684') {
# do_something
}

\$cn = \$pa->complete('240605568_D<<681020_<070510_<_');
# \$cn = '2406055684D<<6810203<0705109<6'

\$cd = \$pa->checkdigit('2406055684D<<6810203<0705109<6');
# \$cd = '6'

\$bn = \$pa->basenumber('2406055684D<<6810203<0705109<6');
# \$bn = '240605568_D<<681020_<070510_<_'

\$aba = CheckDigits('aba_rn');
if (\$aba->is_valid('789456124')) {
# do something
}
``````

# DESCRIPTION

## ALGORITHM

1. Beginning left all digits are weighted with 7,3,1,7,3,1,... for pa_de or 3,7,1,3,7,1,3,7,1 for aba_rn.

2. The sum of those products is computed.

3. For pa_de the checksum is the last digit of the sum from step 2 (modulo 10).

For aba_rn the checksum is the difference of the sum from step 2 to the next multiple of 10.

4. For the german Personalausweis step 1 to 3 is performed for every part of the number and for all 3 parts including the particular checkdigit to compute the total checksum.

If the number solely consists of digits, the checksum is just computed once according to algorithm given above.

## 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>`

# THANKS

Aaron W. West pointed me to a fault in the computing of the check digit. Jim Hickstein made me aware of the ABA routing numbers.

# SEE ALSO

perl, CheckDigits, www.pruefziffernberechnung.de, http://answers.google.com/answers/threadview/id/43619.html, http://www.brainjar.com/js/validation/