Arun Prasaad > Tree-RB-0.500004 > Tree::RB

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NAME ^

Tree::RB - Perl implementation of the Red/Black tree, a type of balanced binary search tree.

VERSION ^

This document describes Tree::RB version 0.500004

SYNOPSIS ^

    use Tree::RB;

    my $tree = Tree::RB->new;
    $tree->put('France'  => 'Paris');
    $tree->put('England' => 'London');
    $tree->put('Hungary' => 'Budapest');
    $tree->put('Ireland' => 'Dublin');
    $tree->put('Egypt'   => 'Cairo');
    $tree->put('Germany' => 'Berlin');

    $tree->put('Alaska' => 'Anchorage'); # D'oh! Alaska isn't a Country
    $tree->delete('Alaska');

    print scalar $tree->get('Ireland'); # 'Dublin'

    print $tree->min->key; # 'Egypt' 
    print $tree->max->key; # 'Ireland' 
    print $tree->size; # 6

    # print items, ordered by key
    my $it = $tree->iter;

    while(my $node = $it->next) {
        printf "key = %s, value = %s\n", $node->key, $node->val;
    }

    # print items in reverse order
    $it = $tree->rev_iter;

    while(my $node = $it->next) {
        printf "key = %s, value = %s\n", $node->key, $node->val;
    }

    # Hash interface
    tie my %capital, 'Tree::RB';

    # or do this to store items in descending order 
    tie my %capital, 'Tree::RB', sub { $_[1] cmp $_[0] };

    $capital{'France'}  = 'Paris';
    $capital{'England'} = 'London';
    $capital{'Hungary'} = 'Budapest';
    $capital{'Ireland'} = 'Dublin';
    $capital{'Egypt'}   = 'Cairo';
    $capital{'Germany'} = 'Berlin';

    # print items in order
    while(my ($key, $val) = each %capital) {
        printf "key = $key, value = $val\n";
    }

DESCRIPTION ^

This is a Perl implementation of the Red/Black tree, a type of balanced binary search tree.

A tied hash interface is also provided to allow ordered hashes to be used.

See the Wikipedia article at http://en.wikipedia.org/wiki/Red-black_tree for more on Red/Black trees.

INTERFACE ^

new([CODEREF])

Creates and returns a new tree. If a reference to a subroutine is passed to new(), the subroutine will be used to override the tree's default lexical ordering and provide a user a defined ordering.

This subroutine should be just like a comparator subroutine used with sort, except that it doesn't do the $a, $b trick.

For example, to get a case insensitive ordering

    my $tree = Tree::RB->new(sub { lc $_[0] cmp lc $_[1]});
    $tree->put('Wall'  => 'Larry');
    $tree->put('Smith' => 'Agent');
    $tree->put('mouse' => 'micky');
    $tree->put('duck'  => 'donald');

    my $it = $tree->iter;

    while(my $node = $it->next) {
        printf "key = %s, value = %s\n", $node->key, $node->val;
    }

resort(CODEREF)

Changes the ordering of nodes within the tree. The new ordering is specified by a comparator subroutine which must be passed to resort().

See "new" for further information about the comparator.

size()

Returns the number of nodes in the tree.

root()

Returns the root node of the tree. This will either be undef if no nodes have been added to the tree, or a Tree::RB::Node object. See the Tree::RB::Node manual page for details on the Node object.

min()

Returns the node with the minimal key.

max()

Returns the node with the maximal key.

lookup(KEY, [MODE])

When called in scalar context, lookup(KEY) returns the value associated with KEY.

When called in list context, lookup(KEY) returns a list whose first element is the value associated with KEY, and whose second element is the node containing the key/value.

An optional MODE parameter can be passed to lookup() to influence which key is returned.

The values of MODE are constants that are exported on demand by Tree::RB

    use Tree::RB qw[LUEQUAL LUGTEQ LULTEQ LUGREAT LULESS LUNEXT LUPREV];
LUEQUAL

Returns node exactly matching the key.

LUGTEQ

Returns the node exactly matching the specified key, if this is not found then the next node that is greater than the specified key is returned.

LULTEQ

Returns the node exactly matching the specified key, if this is not found then the next node that is less than the specified key is returned.

LUGREAT

Returns the node that is just greater than the specified key - not equal to. This mode is similar to LUNEXT except that the specified key need not exist in the tree.

LULESS

Returns the node that is just less than the specified key - not equal to. This mode is similar to LUPREV except that the specified key need not exist in the tree.

LUNEXT

Looks for the key specified, if not found returns undef. If the node is found returns the next node that is greater than the one found (or undef if there is no next node).

This can be used to step through the tree in order.

LUPREV

Looks for the key specified, if not found returns undef. If the node is found returns the previous node that is less than the one found (or undef if there is no previous node).

This can be used to step through the tree in reverse order.

get(KEY)

get() is an alias for lookup().

iter([KEY])

Returns an iterator object that can be used to traverse the tree in order.

The iterator object supports a 'next' method that returns the next node in the tree or undef if all of the nodes have been visited.

See the synopsis for an example.

If a key is supplied, the iterator returned will traverse the tree in order starting from the node with key greater than or equal to the specified key.

    $it = $tree->iter('France');
    my $node = $it->next;
    print $node->key; # -> 'France'

rev_iter([KEY])

Returns an iterator object that can be used to traverse the tree in reverse order.

If a key is supplied, the iterator returned will traverse the tree in order starting from the node with key less than or equal to the specified key.

    $it = $tree->rev_iter('France');
    my $node = $it->next;
    print $node->key; # -> 'France'

    $it = $tree->rev_iter('Finland');
    my $node = $it->next;
    print $node->key; # -> 'England'

hseek(KEY, [{-reverse => 1|0}])

For tied hashes, determines the next entry to be returned by each.

    tie my %capital, 'Tree::RB';

    $capital{'France'}  = 'Paris';
    $capital{'England'} = 'London';
    $capital{'Hungary'} = 'Budapest';
    $capital{'Ireland'} = 'Dublin';
    $capital{'Egypt'}   = 'Cairo';
    $capital{'Germany'} = 'Berlin';
    tied(%capital)->hseek('Germany');

    ($key, $val) = each %capital;
    print "$key, $val"; # -> Germany, Berlin 

The direction of iteration can be reversed by passing a hashref with key '-reverse' and value 1 to hseek after or instead of KEY, e.g. to iterate over the hash in reverse order:

    tied(%capital)->hseek({-reverse => 1});
    $key = each %capital;
    print $key; # -> Ireland 

The following calls are equivalent

    tied(%capital)->hseek('Germany', {-reverse => 1});
    tied(%capital)->hseek({-key => 'Germany', -reverse => 1});

put(KEY, VALUE)

Adds a new node to the tree.

The first argument is the key of the node, the second is its value.

If a node with that key already exists, its value is replaced with the given value and the old value is returned. Otherwise, undef is returned.

delete(KEY)

If the tree has a node with the specified key, that node is deleted from the tree and returned, otherwise undef is returned.

DEPENDENCIES ^

enum

INCOMPATIBILITIES ^

None reported.

BUGS AND LIMITATIONS ^

Please report any bugs or feature requests via the GitHub web interface at https://github.com/arunbear/perl5-scalar-constant/issues.

AUTHOR ^

Arun Prasad <arunbear@cpan.org>

Some documentation has been borrowed from Benjamin Holzman's Tree::RedBlack and Damian Ivereigh's libredblack (http://libredblack.sourceforge.net/).

ACKNOWLEDGEMENTS ^

Thanks for bug reports go to Anton Petrusevich, Wes Thompson, Petre Mierlutiu, Tomer Vromen and Christopher Gurnee.

LICENCE AND COPYRIGHT ^

Copyright (c) 2007, Arun Prasad <arunbear@cpan.org>. All rights reserved.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See perlartistic.

DISCLAIMER OF WARRANTY ^

BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION.

IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

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