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lib/Algorithm/CheckDigits/MXX_006.pm  view on Meta::CPAN

	my $number = shift;

	my $input = shift;
	my $c = 0; # initialize check at 0
	my $digit = 0;
	my $i = 0; my $r;
	foreach $digit (reverse split(//, $number)) {
#		This was jonathans implementation, his permutation
#		table is offset by one compared to the one I already
#		took in MXX_003.pm and reused here
#		$c = $di->[$c]->[$f->[($i+1) % 8]->[$digit]];
		$c = $dieder->[$c]->[$perm->[$i % 8]->[$digit]];
	        $i++;
        }
	return $inverted[$c];
} # _compute_checkdigit()

# Preloaded methods go here.

1;
__END__

=encoding iso-8859-1

=head1 NAME

CheckDigits::MXX_006 - compute check digits with Verhoeff scheme

=head1 SYNOPSIS

  use Algorithm::CheckDigits;

  $verhoeff = CheckDigits('verhoeff');

  if ($verhoeff->is_valid('14567894')) {
	# do something
  }

  $cn = $verhoeff->complete('1456789');
  # $cn = '14567894'

  $cd = $verhoeff->checkdigit('14567894');
  # $cd = '4'

  $bn = $verhoeff->basenumber('14567894');
  # $bn = '1456789'
  
=head1 DESCRIPTION

=head2 ALGORITHM

=over 4

=item 1

Right to left all digits are permutated according to a permutation table.

=item 2

The permutated digits are combined using a diëder table. The first
with the second, the result with the third, this result with the
fourth and so on.

=item 3

The result of the last combination in the diëder table is in such a
way combined that the result is 0 (zero). The number used for this
combination is the checksum.

=back

For details look at the source.

=head2 METHODS

=over 4

=item is_valid($number)

Returns true only if C<$number> consists solely of numbers and the last digit
is a valid check digit according to the algorithm given above.

Returns false otherwise,

=item complete($number)

The check digit for C<$number> is computed and concatenated to the end
of C<$number>.

Returns the complete number with check digit or '' if C<$number>
does not consist solely of digits.

=item basenumber($number)

Returns the basenumber of C<$number> if C<$number> has a valid check
digit.

Return '' otherwise.

=item checkdigit($number)

Returns the checkdigit of C<$number> if C<$number> has a valid check
digit.

Return '' otherwise.

=back

=head2 EXPORT

None by default.

=head1 AUTHOR

Mathias Weidner, C<< <mamawe@cpan.org> >>

=head1 THANKS

Jonathan Peters wrote L<Algorithm::Verhoeff> from which I took the
routine to compute the checkdigits.