graph(n)							Tcl Data Structures							  graph(n)

NAME

       graph - Create and manipulate directed graph objects

SYNOPSIS

       package require Tcl 8.2

       package require struct ?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 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 args 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 ("con-
       nectivity") 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 arcx.

       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  sub-
		     graph 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.

       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 nodex.

       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 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 indi-
	      cates 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 neigh-
	      bors. 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 graph-
	      Name and the name of the current node appended. For a pre-order walk all nodes are Bentered, for a post-order all nodes are left. In
	      a both-order walk the first visit of a node enters it, the second visit leaves it.

KEYWORDS

       graph

struct								       1.2.1								  graph(n)