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# Manual Reference Pages  -  ALGORITHM::CHECKDIGITS::M10_001 (3)

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### NAME

CheckDigits::M10_001 - compute check digits for Bahncard (DE), IMEI, IMEISV, ISIN, Miles&More, Payback (DE), Personnummer (SE), Passport (BR), Credit Cards, SSN (US), Samordningsnummer (SE), VAT RN (ES), VAT RN (IT), VAT RN (SE), International Securities Identifikation Number (ISIN), CUSIP

### 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

```

### DESCRIPTION

#### ALGORITHM

 1. Beginning right all numbers are weighted alternatively 1 and 2 (that is the check digit is weighted 1). 2. The total of the digits of all products is computed. 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 the last digit is a valid check digit according to the algorithm given above. Returns false otherwise, If the checked number is of type CUSIP, the number must be exact 9 digits or letters long and must not have spaces in between. 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>