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# Copyright 2001 Abhijit Menon-Sen <ams@toroid.org>

package Set::Crontab;

use strict;
use Carp;
use vars qw( $VERSION );

$VERSION = '1.03';

sub _expand
{
my (@list, @and, @not);
my ($self, $spec, $range) = @_;

# 1,2-4,*/3,!13,>9,<15
foreach (split /,/, $spec) {
my @pick;
my $step = $1 if s#/(\d+)$##;

# 0+"01" == 1
if (/^(\d+)$/) { push @pick, 0+$1; }
elsif (/^\*$/) { push @pick, @$range; }
elsif (/^(\d+)-(\d+)$/) { push @pick, 0+$1..0+$2; }
elsif (/^!(\d+)$/) { push @not, "\$_ != 0+$1"; }
elsif (/^([<>])(\d+)$/) { push @and, "\$_ $1 0+$2"; }

if ($step) {
my $i;
@pick = grep { defined $_ if $i++ % $step == 0 } @pick;
}

push @list, @pick;
}

if (@and) {
my $and = join q{ && }, @and;
push @list, grep { defined $_ if eval $and } @$range;
}

if (@not) {
my $not = join q{ && }, @not;
@list = grep { defined $_ if eval $not } (@list ? @list : @$range);
}

@list = sort { $a <=> $b } @list;
return \@list;
}

sub _initialise
{
my ($self, $spec, $range) = @_;
return undef unless ref($self);

croak "Usage: ".__PACKAGE__."->new(\$spec, [\@range])"
unless defined $spec && ref($range) eq "ARRAY";

$self->{LIST} = $self->_expand($spec, $range);
$self->{HASH} = {map {$_ => 1} @{$self->{LIST}}};

return $self;
};

sub new
{
my $class = shift;
my $self = bless {}, ref($class) || $class;
return $self->_initialise(@_);
}

sub contains
{
my ($self, $num) = @_;

croak "Usage: \$set->contains(\$num)" unless ref($self) && defined $num;
return exists $self->{HASH}{$num};
}

sub list
{
my $self = shift;

croak "Usage: \$set->list()" unless ref($self);
return @{$self->{LIST}};
}

1;
__END__

=head1 NAME

Set::Crontab - Expand crontab(5)-style integer lists

=head1 SYNOPSIS

$s = Set::Crontab->new("1-9/3,>15,>30,!23", [0..30]);

if ($s->contains(3)) { ... }

=head1 DESCRIPTION

Set::Crontab parses crontab-style lists of integers and defines some
utility functions to make it easier to deal with them.

=head2 Syntax

Numbers, ranges, *, and step values all work exactly as described in
L<crontab(5)>. A few extensions to the standard syntax are described
below.

=over 4

=item < and >

<N selects the elements smaller than N from the entire range, and adds
them to the set. >N does likewise for elements larger than N.

=item !

!N excludes N from the set. It applies to the other specified
range; otherwise it applies to the specified ranges (i.e. "!3" with a
range of "1-10" corresponds to "1-2,4-10", but ">3,!7" in the same range
means "4-6,8-10").

=back

=head2 Functions

=over 4

=item new($spec, [@range])

Creates a new Set::Crontab object and returns a reference to it.

=item contains($num)

Returns true if C<$num> exists in the set.

=item list()

Returns the expanded list corresponding to the set. Elements are in
ascending order.

=back

The functions described above croak if they are called with incorrect
arguments.

=head1 SEE ALSO

L<crontab(5)>

=head1 AUTHOR

Abhijit Menon-Sen <ams@toroid.org>

Copyright 2001 Abhijit Menon-Sen <ams@toroid.org>

This module is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
(1-1/2)