NAME

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

VERSION

version 0.92

SYNOPSIS

    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";
        }
      }

DESCRIPTION

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.

TYPES

new()

    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.

size()

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

Returns the number of elements in the set.

is_empty()

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

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

is_null()

is_null() is an alias to is_empty().

has()/contains()/exists/()

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

Returns true if the set contains the string $member.

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

insert()

    $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)

delete()/remove()

    $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().

members

my @members = $set->members;

This returns an array of set members in an unsorted array.

SEE ALSO

Set::Object, Set::Scalar.

SOURCE

The development version is on github at https://github.com/robrwo/Set-Light and may be cloned from git://github.com/robrwo/Set-Light.git

BUGS

Please report any bugs or feature requests on the bugtracker website https://rt.cpan.org/Public/Dist/Display.html?Name=Set-Light or by email to bug-Set-Light@rt.cpan.org.

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.

AUTHOR

Tels nospam-abuse@bloodgate.com

CONTRIBUTOR

Robert Rothenberg rrwo@cpan.org

COPYRIGHT AND LICENSE

This software is copyright (c) 2004-2008, 2019 by Tels.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.