/**
@defgroup gwrappers Wrapper Classes for Graphs
\brief This group contains several wrapper classes for graphs
@ingroup graphs
The main parts of LEMON are the different graph structures,
generic graph algorithms, graph concepts which couple these, and
graph wrappers. While the previous ones are more or less clear, the
latter notion needs further explanation.
Graph wrappers are graph classes which serve for considering graph
structures in different ways. A short example makes the notion much
clearer.
Suppose that we have an instance \c g of a directed graph
type say \c ListGraph and an algorithm
\code template int algorithm(const Graph&); \endcode
is needed to run on the reversely oriented graph.
It may be expensive (in time or in memory usage) to copy
\c g with the reverse orientation.
Thus, a wrapper class
\code template class RevGraphWrapper; \endcode is used.
The code looks as follows
\code
ListGraph g;
RevGraphWrapper rgw(g);
int result=algorithm(rgw);
\endcode
After running the algorithm, the original graph \c g
remains untouched. Thus the graph wrapper used above is to consider the
original graph with reverse orientation.
This techniques gives rise to an elegant code, and
based on stable graph wrappers, complex algorithms can be
implemented easily.
In flow, circulation and bipartite matching problems, the residual
graph is of particular importance. Combining a wrapper implementing
this, shortest path algorithms and minimum mean cycle algorithms,
a range of weighted and cardinality optimization algorithms can be
obtained. For lack of space, for other examples,
the interested user is referred to the detailed documentation of graph
wrappers.
The behavior of graph wrappers can be very different. Some of them keep
capabilities of the original graph while in other cases this would be
meaningless. This means that the concepts that they are a model of depend
on the graph wrapper, and the wrapped graph(s).
If an edge of \c rgw is deleted, this is carried out by
deleting the corresponding edge of \c g. But for a residual
graph, this operation has no sense.
Let we stand one more example here to simplify your work.
wrapper class
\code template class RevGraphWrapper; \endcode
has constructor
` RevGraphWrapper(Graph& _g)`.
This means that in a situation,
when a ` const ListGraph& ` reference to a graph is given,
then it have to be instantiated with `Graph=const ListGraph`.
\code
int algorithm1(const ListGraph& g) {
RevGraphWrapper rgw(g);
return algorithm2(rgw);
}
\endcode
*/