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#### NAME

```       CheckDigits::M10_004 - compute check digits for 2aus5, EAN, ILN,
ISBN13, NVE
```

#### SYNOPSIS

```         use Algorithm::CheckDigits;

\$ean = CheckDigits('ean');

if (\$ean->is_valid('7622200004607')) {
# do something
}

\$cn = \$ean->complete('762220000460');
# \$cn = '7622200004607'

\$cd = \$ean->checkdigit('7622200004607');
# \$cd = '7'

\$bn = \$ean->basenumber('7622200004607');
# \$bn = '762220000460'
```

#### DESCRIPTION

```   ALGORITHM
1.  Beginning right all numbers are weighted alternatively 1 and 3
(that is the check digit is weighted 1).

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 digits, spaces and
hyphen 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, spaces and hyphen.

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.

EXPORT
None by default.
```

#### BUGS AND LIMITATIONS

```       When invoked as "CheckDigits('isbn13')" the module checks whether the
first three digits (the country code) are 978 or 979, the current (as
of 2006) EAN country codes for books. If at any time other EAN country
codes for ISBN-13 will be specified and the then responsible maintainer
ignores this in the code, please send a friendly email.
```

#### AUTHOR

```       Mathias Weidner, <mathias@weidner.in-bad-schmiedeberg.de>
```

`       perl, CheckDigits, www.pruefziffernberechnung.de.`

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