NAME
Set::String - (memory efficient) unordered set of strings
SYNOPSIS
use Set::String;
my $set = Set::String->new( qw/foo bar baz/ );
if (!$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 '$_'.\n";
}
}DESCRIPTION
Set::String implements an unordered set of strings. Set::String currently uses underneath a hash, and each key of the hash points to the same scalar, thus saving memory per item.
Why not use a hash?
Usually you would use a hash to keep track of a list of items like:
my %SEEN;
...
if (!$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 need one scalar.
Why not use Set::Object or Set::Scalar?
These waste even more memory and/or are slower than an ordinary hash.
METHODS
new()
my $set = Set::String->new();Creates a new Set::String object. An optionally passed hash reference can contain options. Currently no options are supported:
my $set = Set::String->new( { myoption => 1, foobar => 2 });Note that:
my $set = Set::String->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::String;
my $set = Set::String->new();
print $set->insert('foo'); # 1
print $set->insert('foo'); # 0
print $set->insert('bar','baz','foo'); # 2 (foo already inserted)delete()
$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::String;
my $set = Set::String->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().
LICENSE
This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself.
AUTHOR
(c) Tels bloodgate.com 2004.