/*!

\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.

This simple map assigns \f$\pi\f$ to each edge.

\code
class MyMap 
{
  double operator[](Graph::EdgeIt e) const { return 1;}
};
\endcode


Here is a more complex example. It provides a length function which is obtained
from a base length function modified by a potential difference.
\todo Please improve on the english. 

\code
class MyLengthMap 
{
  const Graph::EdgeMap &ol;
  const Graph::NodeMap &pot;
  
  double operator[](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

*/