How to obtain the complement intervals from an array of intervals?

Question

The easiest way to explain my question is with an example.

I have an array in Perl with a set of intervals, and I need to obtain the complementary intervals, in other words, the anti-image of that set. From:

@ary1 = qw(23-44 85-127 168-209)

Printed intervals: 23-44, 85-127, 168-209.

Transform it to:

...-22, 45-84, 128-167, 210-...

Answer 1

If the intervals are already sorted and don't overlap:

#!/usr/bin/perl
use warnings;
use strict;

use List::MoreUtils qw{ natatime };

my @ary1 = qw(23-44 85-127 168-209);

my $diff = 1;
my $pair = natatime 2, '...', 
                       map({ map { $diff *= -1; $_ + $diff }
                                 split /-/
                           } @ary1),
                       '...';
my @compl;
while (my ($from, $to) = $pair->()) {
    push @compl, "$from-$to";
}

print "@compl\n";

Output

...-22 45-84 128-167 210-...