FAQ

#$Id$
Q.  How can I make comparisons among more than two lists when I don't know in
advance how many lists I'll need to compare?

A.  Write a subroutine which returns a reference to an array.  In your
program, call that subroutine as needed.  Push the array reference returned
onto a "list of lists" which is then passed to List::Compare->new().

Example:  You have a function, get_random_integers(), which returns a
reference to a list of random integers between 0 and 9.  The number of items
in the list is itself a random integer between 0 and 9.

    sub get_random_integers {
        my $listsize = int(rand(10));  # 0..9
        my @list;
        for (0 .. $listsize) {
            push @list, int(rand(10));
        }
        return \@list;
    }
    
You call get_random_integers a random number of times between 2 and 11.  Why
2?  Because List::Compare must compare at least two lists. 
    
    #!/usr/bin/perl
    use strict;
    use warnings;
    use List::Compare;
    use Data::Dumper;
    $Data::Dumper::Indent = 0;
    
    my $list_quantity = int(rand(10)) + 2; # must have >= 2 lists
    my @lol;
    for (0 .. $list_quantity) {
        my $listref = get_random_integers();
        print Dumper $listref;
        print "\n";
        push @lol, $listref;
    }
    
    my $lc = List::Compare->new(@lol);
    my (@intersection, @union, @unique, @complement);
    @intersection = $lc->get_intersection();
    @union = $lc->get_union();
    @unique = $lc->get_unique(0);          # items unique to first list
    @complement = $lc->get_complement(0);  # items found in any list but first
    
    print Dumper(\@intersection, \@union, \@unique, \@complement);

Just substitute your own list-generating function for get_random_integers() in
the example above.  For production code, strip out all the calls to Data::Dumper.