modules/struct/graph1.man

[comment {-*- tcl -*-}]
[manpage_begin {struct::graph v1} n 1.2.1]
[copyright {2002 Andreas Kupries <andreas_kupries@users.sourceforge.net>}]
[moddesc   {Tcl Data Structures}]
[titledesc {Create and manipulate directed graph objects}]
[category  {Data structures}]
[require Tcl 8.2]
[require struct::graph [opt 1.2.1]]
[description]
[para]

The [cmd ::struct::graph] command creates a new graph object with an
associated global Tcl command whose name is [arg graphName].  This
command may be used to invoke various operations on the graph.  It has
the following general form:

[list_begin definitions]
[call [cmd graphName] [arg option] [opt [arg "arg arg ..."]]]

[arg Option] and the [arg arg]s determine the exact behavior of the
command.

[list_end]

[para]

A directed graph is a structure containing two collections of
elements, called [emph nodes] and [emph arcs] respectively, together
with a relation ("connectivity") that places a general structure upon
the nodes and arcs.

[para]

Each arc is connected to two nodes, one of which is called the

[emph source] and the other the [emph target]. This imposes a
direction upon the arc, which is said to go from the source to the
target. It is allowed that source and target of an arc are the same
node. Such an arc is called a [emph loop]. Whenever a node is source
or target of an arc both are said to be [emph adjacent]. This extends
into a relation between nodes, i.e. if two nodes are connected through
at least one arc they are said to be [emph adjacent] too.

[para]

Each node can be the source and target for any number of arcs. The
former are called the [emph {outgoing arcs}] of the node, the latter
the [emph {incoming arcs}] of the node. The number of edges in either
set is called the [emph in-] resp. the [emph out-degree] of the node.

[para]

In addition to maintaining the node and arc relationships, this graph
implementation allows any number of keyed values to be associated with
each node and arc.

[para]

The following commands are possible for graph objects:

[list_begin definitions]

[call [arg graphName] [method destroy]]

Destroy the graph, including its storage space and associated command.

[call [arg graphName] [method {arc append}] [arg arc] [opt "-key [arg key]"] [arg value]]

Appends a [arg value] to one of the keyed values associated with an
[arg arc]. If no [arg key] is specified, the key [const data] is
assumed.


[call [arg graphName] [method {arc delete}] [arg arc] [opt "[arg arc] ..."]]

Remove the specified arcs from the graph.


[call [arg graphName] [method {arc exists}] [arg arc]]

Return true if the specified [arg arc] exists in the graph.


[call [arg graphName] [method {arc get}] [arg arc] [opt "-key [arg key]"]]

Return the value associated with the key [arg key] for the [arg arc].
If no key is specified, the key [const data] is assumed.

[call [arg graphName] [method {arc getall}] [arg arc]]

Returns a serialized list of key/value pairs (suitable for use with
[lb][cmd {array set}][rb]) for the [arg arc].


[call [arg graphName] [method {arc keys}] [arg arc]]

Returns a list of keys for the [arg arc].


[call [arg graphName] [method {arc keyexists}] [arg arc] [opt "-key [arg key]"]]

Return true if the specified [arg key] exists for the [arg arc]. If no
[arg key] is specified, the key [const data] is assumed.


[call [arg graphName] [method {arc insert}] [arg start] [arg end] [opt [arg child]]]

Insert an arc named [arg child] into the graph beginning at the node
[arg start] and ending at the node [arg end]. If the name of the new
arc is not specified the system will generate a unique name of the
form [emph arc][arg x].


[call [arg graphName] [method {arc lappend}] [arg arc] [opt "-key [arg key]"] [arg value]]

Appends a [arg value] (as a list) to one of the keyed values
associated with an [arg arc].  If no [arg key] is specified, the key
[const data] is assumed.


[call [arg graphName] [method {arc set}] [arg arc] [opt "-key [arg key]"] [opt [arg value]]]

Set or get one of the keyed values associated with an arc.  If no key
is specified, the key [const data] is assumed.  Each arc that is
added to a graph has the empty string assigned to the key

[const data] automatically.  An arc may have any number of keyed
values associated with it.  If [arg value] is not specified, this
command returns the current value assigned to the key; if [arg value]
is specified, this command assigns that value to the key.


[call [arg graphName] [method {arc source}] [arg arc]]

Return the node the given [arg arc] begins at.


[call [arg graphName] [method {arc target}] [arg arc]]

Return the node the given [arg arc] ends at.


[call [arg graphName] [method {arc unset}] [arg arc] [opt "-key [arg key]"]]

Remove a keyed value from the arc [arg arc].  If no key is specified,
the key [const data] is assumed.


[call [arg graphName] [method arcs] [opt "-key [arg key]"] [opt "-value [arg value]"] [opt "-in|-out|-adj|-inner|-embedding [arg nodelist]"]]

Return a list of arcs in the graph. If no restriction is specified a
list containing all arcs is returned. Restrictions can limit the list
of returned arcs based on the nodes that are connected by the arc, on
the keyed values associated with the arc, or both. The restrictions
that involve connected nodes have a list of nodes as argument,
specified after the name of the restriction itself.

[list_begin definitions]
[def [option -in]]

Return a list of all arcs whose target is one of the nodes in the
[arg nodelist].

[def [option -out]]

Return a list of all arcs whose source is one of the nodes in the
[arg nodelist].

[def [option -adj]]

Return a list of all arcs adjacent to at least one of the nodes in the
[arg nodelist]. This is the union of the nodes returned by

[option -in] and [option -out].

[def [option -inner]]

Return a list of all arcs adjacent to two of the nodes in the

[arg nodelist]. This is the set of arcs in the subgraph spawned by the
specified nodes.

[def [option -embedding]]

Return a list of all arcs adjacent to exactly one of the nodes in the
[arg nodelist]. This is the set of arcs connecting the subgraph
spawned by the specified nodes to the rest of the graph.

[def "[option -key] [arg key]"]

Limit the list of arcs that are returned to those arcs that have an
associated key [arg key].

[def "[option -value] [arg value]"]

This restriction can only be used in combination with

[option -key]. It limits the list of arcs that are returned to those
arcs whose associated key [arg key] has the value [arg value].

[list_end]
[para]

The restrictions imposed by either [option -in], [option -out],
[option -adj], [option -inner], or [option -embedded] are applied
first. Specifying more than one of them is illegal.

At last the restrictions set via [option -key] (and [option -value])
are applied.
Specifying more than one [option -key] (and [option -value]) is
illegal.


[call [arg graphName] [method {node append}] [arg node] [opt "-key [arg key]"] [arg value]]

Appends a [arg value] to one of the keyed values associated with an
[arg node]. If no [arg key] is specified, the key [const data] is
assumed.


[call [arg graphName] [method {node degree}] [opt -in|-out] [arg node]]

Return the number of arcs adjacent to the specified [arg node]. If one
of the restrictions [option -in] or [option -out] is given only the
incoming resp. outgoing arcs are counted.


[call [arg graphName] [method {node delete}] [arg node] [opt "[arg node] ..."]]

Remove the specified nodes from the graph.  All of the nodes' arcs
will be removed as well to prevent unconnected arcs.


[call [arg graphName] [method {node exists}] [arg node]]

Return true if the specified [arg node] exists in the graph.


[call [arg graphName] [method {node get}] [arg node] [opt "-key [arg key]"]]

Return the value associated with the key [arg key] for the [arg node].
If no key is specified, the key [const data] is assumed.

[call [arg graphName] [method {node getall}] [arg node]]

Returns a serialized list of key/value pairs (suitable for use with
[lb][cmd {array set}][rb]) for the [arg node].


[call [arg graphName] [method {node keys}] [arg node]]

Returns a list of keys for the [arg node].


[call [arg graphName] [method {node keyexists}] [arg node] [opt "-key [arg key]"]]

Return true if the specified [arg key] exists for the [arg node]. If
no [arg key] is specified, the key [const data] is assumed.


[call [arg graphName] [method {node insert}] [opt [arg child]]]

Insert a node named [arg child] into the graph. The nodes has no arcs
connected to it. If the name of the new child is not specified the
system will generate a unique name of the form [emph node][arg x].

[call [arg graphName] [method {node lappend}] [arg node] [opt "-key [arg key]"] [arg value]]

Appends a [arg value] (as a list) to one of the keyed values
associated with an [arg node]. If no [arg key] is specified, the key
[const data] is assumed.


[call [arg graphName] [method {node opposite}] [arg node] [arg arc]]

Return the node at the other end of the specified [arg arc], which has
to be adjacent to the given [arg node].


[call [arg graphName] [method {node set}] [arg node] [opt "-key [arg key]"] [opt [arg value]]]

Set or get one of the keyed values associated with a node.  If no key
is specified, the key [const data] is assumed.  Each node that is
added to a graph has the empty string assigned to the key

[const data] automatically.  A node may have any number of keyed
values associated with it.  If [arg value] is not specified, this
command returns the current value assigned to the key; if [arg value]
is specified, this command assigns that value to the key.


[call [arg graphName] [method {node unset}] [arg node] [opt "-key [arg key]"]]

Remove a keyed value from the node [arg node].  If no key is
specified, the key [method data] is assumed.

[call [arg graphName] [method nodes] [opt "-key [arg key]"] [opt "-value [arg value]"] [opt "-in|-out|-adj|-inner|-embedding [arg nodelist]"]]

Return a list of nodes in the graph. Restrictions can limit the list
of returned nodes based on neighboring nodes, or based on the keyed
values associated with the node. The restrictions that involve
neighboring nodes have a list of nodes as argument, specified after
the name of the restriction itself.

[para]

The possible restrictions are the same as for method

[method arcs]. The set of nodes to return is computed as the union of
all source and target nodes for all the arcs satisfying the
restriction as defined for [method arcs].


[call [arg graphName] [method get] [opt "-key [arg key]"]]

Return the value associated with the key [arg key] for the graph. If
no key is specified, the key [const data] is assumed.


[call [arg graphName] [method getall]]

Returns a serialized list of key/value pairs (suitable for use with
[lb][cmd {array set}][rb]) for the whole graph.


[call [arg graphName] [method keys]]

Returns a list of keys for the whole graph.


[call [arg graphName] [method keyexists] [opt "-key [arg key]"]]

Return true if the specified [arg key] exists for the whole graph. If no
[arg key] is specified, the key [const data] is assumed.


[call [arg graphName] [method set] [opt "-key [arg key]"] [opt [arg value]]]

Set or get one of the keyed values associated with a graph. If no key
is specified, the key [const data] is assumed. Each graph has the
empty string assigned to the key [const data] automatically. A graph
may have any number of keyed values associated with it. If [arg value]
is not specified, this command returns the current value assigned to
the key; if [arg value] is specified, this command assigns that value
to the key.


[call [arg graphName] [method swap] [arg node1] [arg node2]]

Swap the position of [arg node1] and [arg node2] in the graph.


[call [arg graphName] [method unset] [opt "-key [arg key]"]]

Remove a keyed value from the graph. If no key is specified, the key
[const data] is assumed.

[call [arg graphName] [method walk] [arg node] [opt "-order [arg order]"] [opt "-type [arg type]"] [opt "-dir [arg direction]"] -command [arg cmd]]

Perform a breadth-first or depth-first walk of the graph starting at
the node [arg node] going in either the direction of outgoing or
opposite to the incoming arcs.

[para]

The type of walk, breadth-first or depth-first, is determined by the
value of [arg type]; [const bfs] indicates breadth-first,

[const dfs] indicates depth-first.  Depth-first is the default.

[para]

The order of the walk, pre-order, post-order or both-order is
determined by the value of [arg order]; [const pre] indicates
pre-order, [const post] indicates post-order, [const both] indicates
both-order. Pre-order is the default. Pre-order walking means that a
node is visited before any of its neighbors (as defined by the

[arg direction], see below). Post-order walking means that a parent is
visited after any of its neighbors. Both-order walking means that a
node is visited before [emph and] after any of its neighbors. The
combination of a bread-first walk with post- or both-order is illegal.

[para]

The direction of the walk is determined by the value of [arg dir];
[const backward] indicates the direction opposite to the incoming
arcs, [const forward] indicates the direction of the outgoing arcs.

[para]

As the walk progresses, the command [arg cmd] will be evaluated at
each node, with the mode of the call ([const enter] or
[const leave]) and values [arg graphName] and the name of the current
node appended. For a pre-order walk, all nodes are [const enter]ed, for a
post-order all nodes are left. In a both-order walk the first visit of
a node [const enter]s it, the second visit [const leave]s it.

[list_end]

[section {BUGS, IDEAS, FEEDBACK}]

This document, and the package it describes, will undoubtedly contain
bugs and other problems.

Please report such in the category [emph {struct :: graph}] of the
[uri {http://sourceforge.net/tracker/?group_id=12883} {Tcllib SF Trackers}].

Please also report any ideas for enhancements you may have for either
package and/or documentation.


[keywords graph cgraph]
[manpage_end]