CheckDigits::M10_001(3) compute check digits for Bahncard (DE), IMEI,

## SYNOPSIS

use Algorithm::CheckDigits;
\$visa = CheckDigits('visa');
if (\$visa->is_valid('4111 1111 1111 1111')) {
# do something
}
\$cn = \$visa->complete('4111 1111 1111 111');
# \$cn = '4111 1111 1111 1111'
\$cd = \$visa->checkdigit('4111 1111 1111 1111');
# \$cd = '7'
\$bn = \$visa->basenumber('4111 1111 1111 1111');
# \$bn = '4111 1111 1111 111'

## ALGORITHM

1.
Beginning right all numbers are weighted alternatively 1 and 2 (that is the check digit is weighted 1).
2.
3.
The sum of step 3 ist taken modulo 10.
4.
The check digit is the difference between 10 and the number from step 3.

To validate the total of the digits of all numbers inclusive check digit taken modulo 10 must be 0.

## 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]>