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
(<#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
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.