skiplist(n)                   Tcl Data Structures                  skiplist(n)





NAME
       skiplist - Create and manipulate skiplists

SYNOPSIS
       package require Tcl  8.2

       package require struct  ??1.3??

       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:

       skiplistName option ?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 balanc-
       ing, 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 proba-
       bilistic 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 delete node ?node...?
              Remove the specified nodes from the skiplist.

       skiplistName destroy
              Destroy the skiplist, including its storage space and associated
              command.

       skiplistName insert key 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 search node ?-key key?
              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 walk cmd
              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.

KEYWORDS
       skiplist

COPYRIGHT
       Copyright (c) 2000 Keith Vetter



struct                                1.3                          skiplist(n)