Home › Tcl Data Structures tcllib
struct::skiplist
Create and manipulate skiplists
literal type exactly as shown
argument replace with your value
?optional? may be omitted
Synopsis#
package require Tcl 8.5 9
package require struct::skiplist ?1.4?
skiplistName option ?arg arg ...?
skiplistName delete node ?node...?
skiplistName destroy
skiplistName insert key value
skiplistName search node ?-key key?
skiplistName size
skiplistName walk cmd
Description#
The ::struct::skiplist command creates a new skiplist object with an associated global Tcl command whose name is skiplistName. This command may be used to invoke various operations on the skiplist. It has the following general form:
skiplistNameoption ?arg arg ...?#-
Option and the args determine the exact behavior of the command.
Skip lists are an alternative data structure to binary trees. They can be used to maintain ordered lists over any sequence of insertions and deletions. Skip lists use randomness to achieve probabilistic balancing, and as a result the algorithms for insertion and deletion in skip lists are much simpler and faster than those for binary trees.
To read more about skip lists see Pugh, William. Skip lists: a probabilistic alternative to balanced trees In: Communications of the ACM, June 1990, 33(6) 668-676.
Currently, the key can be either a number or a string, and comparisons are performed with the built in greater than operator. The following commands are possible for skiplist objects:
- skiplistName
deletenode ?node...? -
Remove the specified nodes from the skiplist.
- skiplistName
destroy -
Destroy the skiplist, including its storage space and associated command.
- skiplistName
insertkey value -
Insert a node with the given key and value into the skiplist. If a node with that key already exists, then the that node's value is updated and its node level is returned. Otherwise a new node is created and 0 is returned.
- skiplistName
searchnode ?-keykey? -
Search for a given key in a skiplist. If not found then 0 is returned. If found, then a two element list of 1 followed by the node's value is retuned.
- skiplistName
size -
Return a count of the number of nodes in the skiplist.
- skiplistName
walkcmd -
Walk the skiplist from the first node to the last. At each node, the command cmd will be evaluated with the key and value of the current node appended.
Bugs, ideas, feedback#
This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category struct :: skiplist of the Tcllib Trackers [http://core.tcl.tk/tcllib/reportlist]. Please also report any ideas for enhancements you may have for either package and/or documentation.
When proposing code changes, please provide unified diffs, i.e the output of diff -u.
Note further that attachments are strongly preferred over inlined patches. Attachments can be made by going to the Edit form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar.
Category#
Data structures
Copyright#
Copyright (c) 2000 Keith Vetter