File Coverage

blib/lib/List/Permutor.pm

Criterion	Covered	Total	%
statement	31	31	100.0
branch	4	4	100.0
condition	3	3	100.0
subroutine	6	6	100.0
pod	4	4	100.0
total	48	48	100.0

package List::Permutor;

use strict;
use vars qw($VERSION @ISA @EXPORT @EXPORT_OK);

require Exporter;

@ISA = qw(Exporter);
@EXPORT = qw();
$VERSION = '0.022';

sub new {
    my $class = shift;
    my $items = [ @_ ];
    bless [ $items, [ 0..$#$items ] ], $class;
}

sub reset {
    my $self = shift;
    my $items = $self->[0];
    $self->[1] = [ 0..$#$items ];
    1;		# No useful return value
}

sub peek {
    my $self = shift;
    my $items = $self->[0];
    my $rv = $self->[1];
    @$items[ @$rv ];
}

sub next {
    my $self = shift;
    my $items = $self->[0];
    my $rv = $self->[1];	# return value array
    return unless @$rv;
    my @next = @$rv;
    # The last N items in @next (for 1 <= N <= @next) are each
    # smaller than the one before. Move those into @tail.
    my @tail = pop @next;
    while (@next and $next[-1] > $tail[-1]) {
        push @tail, pop @next;
    }
    # Then there's one more. Right?
    if (defined(my $extra = pop @next)) {
	# The extra one exchanges with the next larger one in @tail
	my($place) = grep $extra < $tail[$_], 0..$#tail;
	($extra, $tail[$place]) = ($tail[$place], $extra);
	# And the next order is what you get by assembling the three
	$self->[1] = [ @next, $extra, @tail ];
    } else {
        # Guess that's all....
	$self->[1] = [];
    }
    return @$items[ @$rv ];
}

1;
__END__