[ Tcllib Table Of Contents | Tcllib Index ]

# struct::graph_v1(n) 1.2.1 "Tcl Data Structures"

## Name

struct::graph_v1 - Create and manipulate directed graph objects

## Synopsis

- package require
**Tcl 8.2** - package require
**struct::graph ?1.2.1?**

**graphName***option*?*arg arg ...*?*graphName***destroy***graphName***arc append***arc*?-key*key*?*value**graphName***arc delete***arc*?*arc*...?*graphName***arc exists***arc**graphName***arc get***arc*?-key*key*?*graphName***arc getall***arc**graphName***arc keys***arc**graphName***arc keyexists***arc*?-key*key*?*graphName***arc insert***start**end*?*child*?*graphName***arc lappend***arc*?-key*key*?*value**graphName***arc set***arc*?-key*key*? ?*value*?*graphName***arc source***arc**graphName***arc target***arc**graphName***arc unset***arc*?-key*key*?*graphName***arcs**?-key*key*? ?-value*value*? ?-in|-out|-adj|-inner|-embedding*nodelist*?*graphName***node append***node*?-key*key*?*value**graphName***node degree**?-in|-out?*node**graphName***node delete***node*?*node*...?*graphName***node exists***node**graphName***node get***node*?-key*key*?*graphName***node getall***node**graphName***node keys***node**graphName***node keyexists***node*?-key*key*?*graphName***node insert**?*child*?*graphName***node lappend***node*?-key*key*?*value**graphName***node opposite***node**arc**graphName***node set***node*?-key*key*? ?*value*?*graphName***node unset***node*?-key*key*?*graphName***nodes**?-key*key*? ?-value*value*? ?-in|-out|-adj|-inner|-embedding*nodelist*?*graphName***get**?-key*key*?*graphName***getall***graphName***keys***graphName***keyexists**?-key*key*?*graphName***set**?-key*key*? ?*value*?*graphName***swap***node1**node2**graphName***unset**?-key*key*?*graphName***walk***node*?-order*order*? ?-type*type*? ?-dir*direction*? -command*cmd*

## Description

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

**graphName***option*?*arg arg ...*?-
*Option*and the*arg*s determine the exact behavior of the command.

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

Each arc is connected to two nodes, one of which is called the
*source* and the other the *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 *loop*. Whenever a node is
source or target of an arc both are said to be *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
*adjacent* too.

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

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.

The following commands are possible for graph objects:

*graphName***destroy**-
Destroy the graph, including its storage space and associated command.

*graphName***arc append***arc*?-key*key*?*value*-
Appends a

*value*to one of the keyed values associated with an*arc*. If no*key*is specified, the key**data**is assumed. *graphName***arc delete***arc*?*arc*...?-
Remove the specified arcs from the graph.

*graphName***arc exists***arc*-
Return true if the specified

*arc*exists in the graph. *graphName***arc get***arc*?-key*key*?-
Return the value associated with the key

*key*for the*arc*. If no key is specified, the key**data**is assumed. *graphName***arc getall***arc*-
Returns a serialized list of key/value pairs (suitable for use with [

**array set**]) for the*arc*. *graphName***arc keys***arc*-
Returns a list of keys for the

*arc*. *graphName***arc keyexists***arc*?-key*key*?-
Return true if the specified

*key*exists for the*arc*. If no*key*is specified, the key**data**is assumed. *graphName***arc insert***start**end*?*child*?-
Insert an arc named

*child*into the graph beginning at the node*start*and ending at the node*end*. If the name of the new arc is not specified the system will generate a unique name of the form*arc**x*. *graphName***arc lappend***arc*?-key*key*?*value*-
Appends a

*value*(as a list) to one of the keyed values associated with an*arc*. If no*key*is specified, the key**data**is assumed. *graphName***arc set***arc*?-key*key*? ?*value*?-
Set or get one of the keyed values associated with an arc. If no key is specified, the key

**data**is assumed. Each arc that is added to a graph has the empty string assigned to the key**data**automatically. An arc may have any number of keyed values associated with it. If*value*is not specified, this command returns the current value assigned to the key; if*value*is specified, this command assigns that value to the key. *graphName***arc source***arc*-
Return the node the given

*arc*begins at. *graphName***arc target***arc*-
Return the node the given

*arc*ends at. *graphName***arc unset***arc*?-key*key*?-
Remove a keyed value from the arc

*arc*. If no key is specified, the key**data**is assumed. *graphName***arcs**?-key*key*? ?-value*value*? ?-in|-out|-adj|-inner|-embedding*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.

**-in**-
Return a list of all arcs whose target is one of the nodes in the

*nodelist*. **-out**-
Return a list of all arcs whose source is one of the nodes in the

*nodelist*. **-adj**-
Return a list of all arcs adjacent to at least one of the nodes in the

*nodelist*. This is the union of the nodes returned by**-in**and**-out**. **-inner**-
Return a list of all arcs adjacent to two of the nodes in the

*nodelist*. This is the set of arcs in the subgraph spawned by the specified nodes. **-embedding**-
Return a list of all arcs adjacent to exactly one of the nodes in the

*nodelist*. This is the set of arcs connecting the subgraph spawned by the specified nodes to the rest of the graph. **-key***key*-
Limit the list of arcs that are returned to those arcs that have an associated key

*key*. **-value***value*-
This restriction can only be used in combination with

**-key**. It limits the list of arcs that are returned to those arcs whose associated key*key*has the value*value*.

The restrictions imposed by either

**-in**,**-out**,**-adj**,**-inner**, or**-embedded**are applied first. Specifying more than one of them is illegal. At last the restrictions set via**-key**(and**-value**) are applied. Specifying more than one**-key**(and**-value**) is illegal. *graphName***node append***node*?-key*key*?*value*-
Appends a

*value*to one of the keyed values associated with an*node*. If no*key*is specified, the key**data**is assumed. *graphName***node degree**?-in|-out?*node*-
Return the number of arcs adjacent to the specified

*node*. If one of the restrictions**-in**or**-out**is given only the incoming resp. outgoing arcs are counted. *graphName***node delete***node*?*node*...?-
Remove the specified nodes from the graph. All of the nodes' arcs will be removed as well to prevent unconnected arcs.

*graphName***node exists***node*-
Return true if the specified

*node*exists in the graph. *graphName***node get***node*?-key*key*?-
Return the value associated with the key

*key*for the*node*. If no key is specified, the key**data**is assumed. *graphName***node getall***node*-
Returns a serialized list of key/value pairs (suitable for use with [

**array set**]) for the*node*. *graphName***node keys***node*-
Returns a list of keys for the

*node*. *graphName***node keyexists***node*?-key*key*?-
Return true if the specified

*key*exists for the*node*. If no*key*is specified, the key**data**is assumed. *graphName***node insert**?*child*?-
Insert a node named

*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*node**x*. *graphName***node lappend***node*?-key*key*?*value*-
Appends a

*value*(as a list) to one of the keyed values associated with an*node*. If no*key*is specified, the key**data**is assumed. *graphName***node opposite***node**arc*-
Return the node at the other end of the specified

*arc*, which has to be adjacent to the given*node*. *graphName***node set***node*?-key*key*? ?*value*?-
Set or get one of the keyed values associated with a node. If no key is specified, the key

**data**is assumed. Each node that is added to a graph has the empty string assigned to the key**data**automatically. A node may have any number of keyed values associated with it. If*value*is not specified, this command returns the current value assigned to the key; if*value*is specified, this command assigns that value to the key. *graphName***node unset***node*?-key*key*?-
Remove a keyed value from the node

*node*. If no key is specified, the key**data**is assumed. *graphName***nodes**?-key*key*? ?-value*value*? ?-in|-out|-adj|-inner|-embedding*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.

The possible restrictions are the same as for 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**arcs**. *graphName***get**?-key*key*?-
Return the value associated with the key

*key*for the graph. If no key is specified, the key**data**is assumed. *graphName***getall**-
Returns a serialized list of key/value pairs (suitable for use with [

**array set**]) for the whole graph. *graphName***keys**-
Returns a list of keys for the whole graph.

*graphName***keyexists**?-key*key*?-
Return true if the specified

*key*exists for the whole graph. If no*key*is specified, the key**data**is assumed. *graphName***set**?-key*key*? ?*value*?-
Set or get one of the keyed values associated with a graph. If no key is specified, the key

**data**is assumed. Each graph has the empty string assigned to the key**data**automatically. A graph may have any number of keyed values associated with it. If*value*is not specified, this command returns the current value assigned to the key; if*value*is specified, this command assigns that value to the key. *graphName***swap***node1**node2*-
Swap the position of

*node1*and*node2*in the graph. *graphName***unset**?-key*key*?-
Remove a keyed value from the graph. If no key is specified, the key

**data**is assumed. *graphName***walk***node*?-order*order*? ?-type*type*? ?-dir*direction*? -command*cmd*-
Perform a breadth-first or depth-first walk of the graph starting at the node

*node*going in either the direction of outgoing or opposite to the incoming arcs.The type of walk, breadth-first or depth-first, is determined by the value of

*type*;**bfs**indicates breadth-first,**dfs**indicates depth-first. Depth-first is the default.The order of the walk, pre-order, post-order or both-order is determined by the value of

*order*;**pre**indicates pre-order,**post**indicates post-order,**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*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*and*after any of its neighbors. The combination of a bread-first walk with post- or both-order is illegal.The direction of the walk is determined by the value of

*dir*;**backward**indicates the direction opposite to the incoming arcs,**forward**indicates the direction of the outgoing arcs.As the walk progresses, the command

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

## Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly
contain bugs and other problems. Please report such in the category
*struct :: graph* of the Tcllib Trackers. Please
also report any ideas for enhancements you may have for either
package and/or documentation.

## Category

Data structures

## Copyright

Copyright © 2002 Andreas Kupries <andreas_kupries@users.sourceforge.net>