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lib/Algorithm/LUHN.pm  view on Meta::CPAN

    print "$_ => $vc{$_}\n";
  }

  Algorithm::LUHN::valid_chars(map {$_ => ord($_)-ord('A')+10} A..Z);
  $c = check_digit("A2C4E6G8");
  print "It worked again\n" if is_valid("A2C4E6G8$c");

=head1 DESCRIPTION

This module calculates the Modulus 10 Double Add Double checksum, also known as
the LUHN Formula. This algorithm is used to verify credit card numbers and
Standard & Poor's security identifiers such as CUSIP's and CSIN's.

You can find plenty of information about the algorithm by searching the web for
"modulus 10 double add double".

=head1 FUNCTION

=over 4

=cut

=item is_valid CHECKSUMMED_NUM

This function takes a credit-card number and returns true if
the number passes the LUHN check.

Ie it returns true if the final character of CHECKSUMMED_NUM is the
correct checksum for the rest of the number and false if not. Obviously the
final character does not factor into the checksum calculation. False will also
be returned if NUM contains in an invalid character as defined by
valid_chars(). If NUM is not valid, $Algorithm::LUHN::ERROR will contain the
reason.

This function is equivalent to

lib/Algorithm/LUHN.pm  view on Meta::CPAN

1;

__END__

=head1 SEE ALSO

L<Algorithm::CheckDigits> provides a front-end to a large collection
of modules for working with check digits.

L<Business::CreditCard> provides three functions for checking credit
card numbers. L<Business::CreditCard::Object> provides an OO interface
to those functions.

L<Business::CardInfo> provides a class for holding credit card details,
and has a type constraint on the card number, to ensure it passes the
LUHN check.

L<Business::CCCheck> provides a number of functions for checking
credit card numbers.

L<Regexp::Common> supports combined LUHN and issuer checking
against a card number.

L<Algorithm::Damm> implements a different kind of check digit algorithm,
the L<Damm algorithm|https://en.wikipedia.org/wiki/Damm_algorithm>
(Damm, not Damn).

L<Math::CheckDigits> implements yet another approach to check digits.