---
name: "Algorithm::CheckDigits::MXX_002"
section: "3pm"
platform: "linux"
package: "libalgorithm-checkdigits-perl"
version: "1.3.6-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/Algorithm::CheckDigits::MXX_002"
---

# Algorithm::CheckDigits::MXX\_002(3pm)

compute check digits for CAS

## NAME

CheckDigits::MXX\_002 - compute check digits for CAS

## SYNOPSIS

```
  use Algorithm::CheckDigits;
  $cas = CheckDigits('cas');
  if ($cas->is_valid('1333-74-0')) {
        # do something
  }
  $cn = $cas->complete('1333-74-');
  # $cn = '1333-74-0'
  $cd = $cas->checkdigit('1333-74-0');
  # $cd = '0'
  $bn = $cas->basenumber('1333-74-0');
  # $bn = '1333-74-'
```

## DESCRIPTION

### ALGORITHM

- 1\.

  Beginning right with the second digit all digits are weighted ascending starting with 1.

- 2\.

  The sum of those products is computed.

- 3\.

  The checksum is the last digit of the sum from step 2 (modulo 10).

### 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.

### EXPORT

None by default.

## AUTHOR

Mathias Weidner, `"<mamawe@cpan.org>"`

## THANKS

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

HERMIER Christophe made me aware that CAS is now assigning 10-digit CAS Registry Numbers (*http://www.cas.org/newsevents/10digitrn.html*)

## SEE ALSO

perl, CheckDigits, *www.pruefziffernberechnung.de*, *www.cas.org* *http://www.cas.org/expertise/cascontent/registry/checkdig.html*