NAME

Algorithm::Damm - Calculate the Damm error correction check digit.

SYNOPSIS

``````  use Algorithm::Damm qw/check_digit is_valid/;

\$c = check_digit("43881234567");
print "It works\n" if is_valid("43881234567\$c");``````

DESCRIPTION

This module implements the Damm algorithm for calculating a check digit.

You can find information about the algorithm by searching the web for "Damm ECC". In particular, see the "SEE ALSO" section (below).

FUNCTIONS

is_valid CHECKSUMMED_NUM

This function returns 1 if the final character of CHECKSUMMED_NUM is the correct checksum for the rest of the number, 0 if not, and undef if CHECKSUMMED_NUM contains an invalid character or does not contain at least two digits (one for the number, and one for the checksum).

This function is equivalent to

``  substr \$N,length(\$N)-1 eq check_digit(substr \$N,0,length(\$N)-1)``

Additionally, due to the way this algorithm works, if you crank the checksum calculation through the last digit (checkdigit included), you will end up with a value of 0.

check_digit NUM

This function returns the checksum of the given number. It will return undef if it is not able to calculate the checksum.

HISTORY

This module came about as I was reverse engineering a checksum method being used on another project of mine. History of the method used was lost to the sands of time, and I needed something to run some quick tests on various checksum algorithms.

This module is a reimplementation of one of the algorithms I had tested.

SEE ALSO

Algorithm::CheckDigits

Algorithm::CheckDigits is a module that this probably should have been written as a part of. There is an open issue (https://github.com/MidLifeXis/perl-algorithm-damm/issues/1) to add an integration layer for this module to Algorithm::CheckDigits.

Algorithm::LUHN

Original code based on Algorithm::LUHN by Tim Ayers.

Math::CheckDigits

Slightly different approach to generating check digits.

Wikipedia

http://en.wikipedia.org/wiki/Damm_algorithm - Article explaining the Damm error correction algorithm.

REPOSITORY

You can find the source at https://www.github.org/MidLifeXis/perl-algorithm-damm.

BUGS

None known at this time, but feel free to submit them to RT or the issue tracker for this source at GitHub.

AUTHOR

This module was written by Brian T. Wightman (http://search.cpan.org/search?author=MLX) based on the module Algorithm::LUHN by Tim Ayers.

Copyright (c) 2013 Brian T. Wightman. All rights reserved.

LICENSE

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.