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# Manual Reference Pages  -  ALGORITHM::CHECKDIGITS::M09_001 (3)

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### NAME

CheckDigits::M09_001 - compute check digits for Euro notes

### SYNOPSIS

```

use Algorithm::CheckDigits;

\$euro = CheckDigits(euronote);

if (\$euro->is_valid(X07738250357)) {
# do something
}

\$cn = \$euro->complete(X0773825035);     # \$cn = X07738250357

\$cd = \$euro->checkdigit(X07738250357); # \$cd = 7

\$bn = \$euro->basenumber(X07738250357); # \$bn = X0773825035

```

### DESCRIPTION

#### ALGORITHM

 1. Letters are replaced with their position in the alphabet (’A’ = 1, ...). 2. The total of the digits of all numbers is computed. 3. This sum is taken modulo 9. 4. The check digit is the difference between 8 and the number of step 3.
To validate the last digit of the total of the digits of all numbers inclusive check digit must be 8.

#### 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. 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>