Version 5.0 The LEDA User Manual

has a source and a target. These are objects of type gml int with path graph.edge.source
and graph.edge.target, respectively. The integer values of source and target refer to node
identifiers. There are some global graph attributes, too. An object of type gml int with
path graph.directed determines whether the graph is undirected (value 0) or directed
(every other integer). The type of node parameters and edge parameters in parameterized
graph (see manual page GRAPH) can be given by objects of type gml string
with path graph.nodeT ype and graph.edgeT ype, respectively. Parameters of nodes and
edges are represented by objects of type gml string with path graph.node.parameter and
graph.edge.parameter, respectively.
No list has to be in a specific order, e.g., you can freely mix node and edge objects in
the graph list. If there are several objects in a class where just one object is required like
graph.node.id, only the last such object is taken into account.
Objects in classes with no predefined rules are simply ignored. This means that an
application A might add specific objects to a graph description in GML format and this
description is still readable for another application B which simply does not care about
the objects which are specific for A.
This parser supports reading user defined objects by providing a mechanism for dealing
with those objects by means of callback functions. You can specify a rule for, e.g., objects
with path graph.node.weight and type gml double like in the following code fragment.
...
bool get node weight(const gml object* gobj, graph* G, node v)
{
double w = gobj->get double();
do something with w, the graph and the corresponding node v
return true; or false if the operation failed
}
...
main()
{
char* filename;
...
graph G;
gml graph parser(G);
parser.append("graph"); parser.append("node");
parser.append("weight");
parser.add node rule for cur path(get node weight,gml double);
// or short parser.add node rule(get node weight,gml double,"weight");
bool parsing ok = parser.parse(filename);
...
}
You can add rules for the graph, for nodes, and for edges. The difference between
them is the type. The type of node rules is as in the example above