CheckDigits::MXX_001(3) compute check digits for PA (DE)

## SYNOPSIS

use Algorithm::CheckDigits;
\$pa = CheckDigits('pa_de');
if (\$pa->is_valid('2406055684D<<6810203<0705109<6')) {
# 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_<_'

## ALGORITHM

1.
Beginning left all digits are weighted with 7,3,1,7,3,1,...
2.
The sum of those products is computed.
3.
The checksum is the last digit of the sum from step 2 (modulo 10).
4.
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.

## 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]>

## THANKS

Aaron W. West pointed me to a fault in the computing of the check digit.