/*!

 \page maps How to write maps

 \section read-maps Readable Maps

 It is quite easy to write your own readmap for the edges or nodes of a graph.

 You can find some example below.

 \code

 class MyMap 

 {

   double get(Graph::EdgeIt e) { return 1;}

 };

 \endcode

 A more complex example

 \code

 class MyLengthMap 

 {

   const Graph::EdgeMap &ol;

   const Graph::NodeMap &pot;

   double get(Graph::EdgeIt e) const { return ol.get(e)-pot.get(v)-pot.get(u);}

   MyComplexMap(const Graph::EdgeMap &o,const Graph::NodeMap &p) :

     ol(o), pot(p);

 };

 \endcode

 */