NAME
    Algorithm::SkipList - Perl implementation of skip lists

REQUIREMENTS
    Perl 5.6.1 is required.

    The following non-standard modules are required:

      enum

Installation
    Installation can be done using the traditional Makefile.PL or the
    newer Build.PL methods.

    Using Makefile.PL:

      perl Makefile.PL
      make
      make test
      make install

    (On Windows platforms you should use nmake instead.)

    Using Build.PL (if you have Module::Build installed):

      perl Build.PL
      perl Build
      perl Build test
      perl Build install    

SYNOPSIS
      my $list = new Algorithm::SkipList();

      $list->insert( 'key1', 'value' );
      $list->insert( 'key2', 'another value' );

      $value = $list->find('key2');

      $list->delete('key1');

DESCRIPTION
    This is an implementation of skip lists in Perl.  What are "skip
    lists"?

      Skip lists are a probabilistic data structure that seem likely
      to supplant balanced trees as the implementation method of
      choice for many applications. Skip list algorithms have the same
      asymptotic expected time bounds as balanced trees and are
      simpler, faster and use less space.(*)

    This implementation may not be faster or use less space, but in
    superficial testing, it does appear to be a reasonably faster
    substitute for some pure-Perl tree modules.  (However, see the
    included Benchmark.txt file for comparisons with similar Perl
    modules, as well as the SEE ALSO section below.)

    Skip lists are similar to linked lists, except that they have
    random links at various levels that allow searches to skip over
    sections of the list, like so:

      4 +---------------------------> +----------------------> +
        |                             |                        |
      3 +------------> +------------> +-------> +-------> +--> +
        |              |              |         |         |    |
      2 +-------> +--> +-------> +--> +--> +--> +-------> +--> +
        |         |    |         |    |    |    |         |    |
      1 +--> +--> +--> +--> +--> +--> +--> +--> +--> +--> +--> +
             A    B    C    D    E    F    G    H    I    J   NIL

    A search would start at the top level: if the link to the right
    exceeds the target key, then it descends a level.

    More information is available in the module documentation.

    (*) Bill Pugh, inventor of skip lists.  Quoted from WikiPedia
        <http://en.wikipedia.org/wiki/Skip_list>

REVISION HISTORY
    Changes since v1.01:

    1.02 Wed Jan  4 2005
	* removed validate_key and validate_value methods from node types
	- removed commented-out assertions
	- added _search_nodes method
	- keys and values methods rewritten, and can retrieve keys or
	  values between key ranges ranges 
	- copy method rewritten
	- corrected typo in error message
	- added missing test to MANIFEST
	- added additional tests
	- added SIGNATURE to distribution

    A detailed revision history is in the Changes file included with
    this distribution.

KNOWN ISSUES
  The following issues are known:

  * If you are upgrading a prior version of List::SkipList, then
    you may want to uninstall the module before installing
    Algorithm::SkipList, so as to remove unused autoloading files.

  * Skip lists are non-deterministic.  Because of this, bugs in programs
    that use this module may be subtle and difficult to reproduce without
    many repeated attempts.

  See http://rt.cpan.org for any additional issues.

AUTHOR
    Robert Rothenberg <rrwo at cpan.org>

LICENSE
    Copyright (c) 2003-2005 Robert Rothenberg. All rights reserved. This
    program is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.

SEE ALSO
    See the article "A Skip List Cookbook" (William Pugh, 1989), or
    similar ones by the author at http://www.cs.umd.edu/~pugh/ which
    discuss skip lists.

    Because of the way Perl manages memory, you may be better off
    using a hash with sorted keys (such as Tie::Hash::Sorted) rather
    than maintaining a sorted dictionary using this or similar
    modules.
