alpar@202: /*!
alpar@202: 
alpar@289: \page maps How to write your own maps
alpar@202: 
alpar@202: \section read-maps Readable Maps
alpar@202: 
alpar@289: The readable maps are very frequently used as the input of the
alpar@289: algorithms.  For this purpose the most straightforward is to use the
alpar@289: maps provided by Hugo's graph structres. Very often however, it is more
alpar@289: convenient and/or more efficient to write your own readable map.
alpar@202: 
alpar@202: You can find some example below.
alpar@202: 
alpar@204: This simple map assigns \f$\pi\f$ to each edge.
alpar@204: 
alpar@202: \code
alpar@273: struct MyMap 
alpar@202: {
alpar@273:   typedef double ValueType;
alpar@289:   double operator[](Graph::Edge e) const { return M_PI;}
alpar@204: };
alpar@204: \endcode
alpar@204: 
alpar@289: An alternative way to define maps. For this, \c MapBase seems to
alpar@289: be a better name then \c NullMap
alpar@289: 
alpar@289: \code
alpar@289: struct MyMap : public MapBase<Edge,double>
alpar@289: {
alpar@289:   double operator[](Graph::Edge e) const { return M_PI;}
alpar@289: };
alpar@289: \endcode
alpar@289: 
alpar@290: Or, if we had \c KeyType and \c ValueType
alpar@289: 
alpar@289: \code
alpar@289: struct MyMap : public MapBase<Edge,double>
alpar@289: {
alpar@289:   ValueType operator[](KeyType e) const { return M_PI;}
alpar@289: };
alpar@289: \endcode
alpar@289: 
alpar@204: 
alpar@210: Here is a more complex example. It provides a length function which is obtained
alpar@210: from a base length function modified by a potential difference.
alpar@202: 
alpar@202: \code
alpar@202: class MyLengthMap 
alpar@202: {
alpar@202:   const Graph::EdgeMap &ol;
alpar@202:   const Graph::NodeMap &pot;
alpar@202:   
alpar@273: public:
alpar@273:   typedef double ValueType;
alpar@273: 
alpar@289:   double operator[](Graph::Edge e) const {
alpar@210:     return ol.get(e)-pot.get(v)-pot.get(u);
alpar@210:   }
alpar@202:   
alpar@202:   MyComplexMap(const Graph::EdgeMap &o,const Graph::NodeMap &p) :
alpar@202:     ol(o), pot(p);
alpar@202: };
alpar@202: \endcode
alpar@202: 
alpar@289: \todo Please improve on the english. 
alpar@273: \todo Don't we need \e to \e require a 'typedef xxx KeyType' tag, as well?
alpar@202: */