Set::Light - (memory efficient) unordered set of strings


        use Set::Light;

        my $set = Set::Light->new( qw/foo bar baz/ );

        if (!$set->is_empty())
          print "Set has ", $set->size(), " elements.\n";
          for (qw/umpf foo bar baz bam/)
            print "Set does ";
            print " not " unless $set->has($_);
            print "contain '$_'.\n";


Set::Light implements an unordered set of strings. Set::Light currently uses underneath a hash, and each key of the hash points to the same scalar, thus saving memory per item.

Why not use a hash?

Usually you would use a hash to keep track of a list of items like:

        my %SEEN;
        if (!$SEEN->{$item}++)
          # haven't seen item before

While this is very fast (both on inserting items, as well as looking them up), it wastes quite a lot of memory, since each key in %SEEN needs one scalar.

Why not use Set::Object or Set::Scalar?

These waste even more memory and/or are slower than an ordinary hash.



        my $set = Set::Light->new();

Creates a new Set::Light object. An optionally passed hash reference can contain options. Currently no options are supported:

        my $set = Set::Light->new( { myoption => 1, foobar => 2 });

Note that:

        my $set = Set::Light->new( qw/for bar baz/);

will create a set with the members for, bar and baz.


        my $elems = $set->size();

Returns the number of elements in the set.


        if (!$set->is_empty()) { ... }

Returns true if the set is empty (has zero elements).


is_null() is an alias to is_empty().


        if ($set->has($member)) { ... }

Returns true if the set contains the string $member.

contains() and exists() are aliases to has().


        $set->insert( $string );
        $set->insert( @strings );

Inserts one or more strings into the set. Returns the number of insertions it really did. Elements that are already contained in the set do not get inserted twice. So:

        use Set::Light;
        my $set = Set::Light->new();
        print $set->insert('foo');              # 1
        print $set->insert('foo');              # 0
        print $set->insert('bar','baz','foo');  # 2     (foo already inserted)


        $set->delete( $string );
        $set->delete( @strings );

Deletes one or more strings from the set. Returns the number of deletions it really did. Elements that are not contained in the set cannot be deleted. So:

        use Set::Light;
        my $set = Set::Light->new();
        print $set->insert('foo','bar');        # 2
        print $set->delete('foo','foo');        # 1     (only once deleted)
        print $set->delete('bar','foo');        # 1     (only once deleted)

remove() is an alias for delete().


This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself.


(c) Tels 2004 - 2008.


Set::Object, Set::Scalar.