diff -r f47faf6913ab -r 09af6d2b683b doc/maps2.dox
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/doc/maps2.dox	Mon Sep 04 20:07:37 2006 +0000
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+/**
+\page maps2 Maps II.
+
+Here we discuss some advanced map techniques. Like writing your own maps or how to
+extend/modify a maps functionality with adaptors.
+
+\section custom_maps Writing Custom ReadMap
+\subsection custom_read_maps Readable Maps
+
+Readable maps are very frequently used as the input of an
+algorithm.  For this purpose the most straightforward way is the use of the
+default maps provided by LEMON's graph structures.
+Very often however, it is more
+convenient and/or more efficient to write your own readable map.
+
+You can find some examples below. In these examples \c Graph is the
+type of the particular graph structure you use.
+
+
+This simple map assigns \f$\pi\f$ to each edge.
+
+\code
+struct MyMap 
+{
+  typedef double Value;
+  typedef Graph::Edge Key;
+  double operator[](Key e) const { return M_PI;}
+};
+\endcode
+
+An alternative way to define maps is to use MapBase
+
+\code
+struct MyMap : public MapBase<Graph::Edge,double>
+{
+  Value operator[](Key e) const { return M_PI;}
+};
+\endcode
+
+Here is a bit more complex example.
+It provides a length function obtained
+from a base length function shifted by a potential difference.
+
+\code
+class ReducedLengthMap  : public MapBase<Graph::Edge,double>
+{
+  const Graph &g;
+  const Graph::EdgeMap<double> &orig_len;
+  const Graph::NodeMap<double> &pot;
+  
+public:
+  Value operator[](Key e) const {
+    return orig_len[e]-(pot[g.target(e)]-pot[g.source(e)]);
+  }
+  
+  ReducedLengthMap(const Graph &_g,
+                   const Graph::EdgeMap &_o,
+                   const Graph::NodeMap &_p)
+    : g(_g), orig_len(_o), pot(_p) {};
+};
+\endcode
+
+Then, you can call e.g. Dijkstra algoritm on this map like this:
+\code
+  ...
+  ReducedLengthMap rm(g,len,pot);
+  Dijkstra<Graph,ReducedLengthMap> dij(g,rm);
+  dij.run(s);
+  ...
+\endcode
+
+*/