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package Algorithm::CheckDigits::M07_001;
use 5.006;
use strict;
use warnings;
our @ISA = qw(Algorithm::CheckDigits);
sub new {
my $proto = shift;
my $class = ref($proto) || $proto;
return bless({}, $class);
} # new()
sub is_valid {
my ($self,$number) = @_;
if ($number =~ /^([0-9]*)([0-9])$/) {
return ($2 == _compute_checkdigit($1));
}
return 0;
} # is_valid()
sub complete {
my ($self,$number) = @_;
if ($number =~ /^([0-9]*)$/) {
return $number . _compute_checkdigit($1);
}
return undef;
} # complete()
sub basenumber {
my ($self,$number) = @_;
if ($number =~ /^([0-9]*)([0-9])$/) {
return $1 if ($2 == _compute_checkdigit($1));
}
return undef;
} # basenumber()
sub checkdigit {
my ($self,$number) = @_;
if ($number =~ /^([0-9]*)([0-9])$/) {
return $2 if ($2 == _compute_checkdigit($1));
}
return undef;
} # checkdigit()
sub _compute_checkdigit {
my $number = shift;
my @digits = split(//,$number);
my $even = 0;
my $sum = 0;
foreach my $digit (@digits) {
$sum += $digit;
$sum += $digit if ($even);
$even = not $even;
}
return $sum % 7;
} # _compute_checkdigit()
# Preloaded methods go here.
1;
__END__
=head1 NAME
CheckDigits::M07_001 - compute check digits modulo 7 method 1
=head1 SYNOPSIS
use Algorithm::CheckDigits;
$m001 = CheckDigits('m001');
if ($m001->is_valid('1234567892')) {
# do something
}
$cn = $m001->complete('123456789'); # $cn = '1234567892'
$cd = $m001->checkdigit('1234567892'); # $cd = '2'
$bn = $m001->basenumber('1234567892'); # $bn = '123456789'
=head1 DESCRIPTION
=head2 ALGORITHM
=over 4
=item 1.
All digits are added.
=item 2.
All digits at even positions are added.
=item 3.
The sum of step 1 and 2 is taken modulo 7.
=item 4.
This is the check digit.
=back
=head2 METHODS
=over 4
=item is_valid($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 undef 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 undef otherwise.
=item checkdigit($number)
Returns the check digit belonging to C<$number> or undef if C<$number> does
not consist solely of digits.
=back
=head2 EXPORT
None by default.
=head1 AUTHOR
Mathias Weidner, E<lt>mathias@weidner.in-bad-schmiedeberg.deE<gt>
=head1 SEE ALSO
L<perl>, F<www.pruefziffernberechnung.de>.
=cut
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