'\"
'\" Generated from file 'skiplist\&.man' by tcllib/doctools with format 'nroff'
'\" Copyright (c) 2000 Keith Vetter
'\"
.TH "struct::skiplist" n 1\&.4 tcllib "Tcl Data Structures"
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.BS
.SH NAME
struct::skiplist \- Create and manipulate skiplists
.SH SYNOPSIS
package require \fBTcl 8\&.5 9\fR
.sp
package require \fBstruct::skiplist ?1\&.4?\fR
.sp
\fBskiplistName\fR \fIoption\fR ?\fIarg arg \&.\&.\&.\fR?
.sp
\fIskiplistName\fR \fBdelete\fR \fInode\fR ?\fInode\fR\&.\&.\&.?
.sp
\fIskiplistName\fR \fBdestroy\fR
.sp
\fIskiplistName\fR \fBinsert\fR \fIkey value\fR
.sp
\fIskiplistName\fR \fBsearch\fR \fInode\fR ?\fB-key\fR \fIkey\fR?
.sp
\fIskiplistName\fR \fBsize\fR
.sp
\fIskiplistName\fR \fBwalk\fR \fIcmd\fR
.sp
.BE
.SH DESCRIPTION
.PP
The \fB::struct::skiplist\fR command creates a new skiplist object
with an associated global Tcl command whose name is
\fIskiplistName\fR\&. This command may be used to invoke various
operations on the skiplist\&. It has the following general form:
.TP
\fBskiplistName\fR \fIoption\fR ?\fIarg arg \&.\&.\&.\fR?
\fIOption\fR and the \fIarg\fRs determine the exact behavior of the
command\&.
.PP
.PP
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\&.
.PP
To read more about skip lists see Pugh, William\&.
\fISkip lists: a probabilistic alternative to balanced trees\fR
In: Communications of the ACM, June 1990, 33(6) 668-676\&.
.PP
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:
.TP
\fIskiplistName\fR \fBdelete\fR \fInode\fR ?\fInode\fR\&.\&.\&.?
Remove the specified nodes from the skiplist\&.
.TP
\fIskiplistName\fR \fBdestroy\fR
Destroy the skiplist, including its storage space and associated command\&.
.TP
\fIskiplistName\fR \fBinsert\fR \fIkey value\fR
Insert a node with the given \fIkey\fR and \fIvalue\fR 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\&.
.TP
\fIskiplistName\fR \fBsearch\fR \fInode\fR ?\fB-key\fR \fIkey\fR?
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\&.
.TP
\fIskiplistName\fR \fBsize\fR
Return a count of the number of nodes in the skiplist\&.
.TP
\fIskiplistName\fR \fBwalk\fR \fIcmd\fR
Walk the skiplist from the first node to the last\&. At each node, the
command \fIcmd\fR will be evaluated with the key and value of the
current node appended\&.
.PP
.SH "BUGS, IDEAS, FEEDBACK"
This document, and the package it describes, will undoubtedly contain
bugs and other problems\&.
Please report such in the category \fIstruct :: skiplist\fR of the
\fITcllib Trackers\fR [http://core\&.tcl\&.tk/tcllib/reportlist]\&.
Please also report any ideas for enhancements you may have for either
package and/or documentation\&.
.PP
When proposing code changes, please provide \fIunified diffs\fR,
i\&.e the output of \fBdiff -u\fR\&.
.PP
Note further that \fIattachments\fR are strongly preferred over
inlined patches\&. Attachments can be made by going to the \fBEdit\fR
form of the ticket immediately after its creation, and then using the
left-most button in the secondary navigation bar\&.
.SH KEYWORDS
skiplist
.SH CATEGORY
Data structures
.SH COPYRIGHT
.nf
Copyright (c) 2000 Keith Vetter

.fi
