diff -r 467d7927a901 -r 3f63d9db307b lemon/lemon_writer.h
--- a/lemon/lemon_writer.h	Wed Oct 05 13:17:42 2005 +0000
+++ b/lemon/lemon_writer.h	Wed Oct 05 13:18:51 2005 +0000
@@ -35,6 +35,7 @@
 #include <lemon/bits/item_writer.h>
 #include <lemon/utility.h>
 #include <lemon/maps.h>
+#include <lemon/xy.h>
 
 #include <lemon/concept_check.h>
 #include <lemon/concept/maps.h>
@@ -84,6 +85,85 @@
 
     };
 
+    template <typename Map>
+    struct Ref { typedef const Map& Type; };
+
+    template <typename Graph, typename Map>
+    class ForwardComposeMap {
+    public:
+      typedef typename Graph::UndirEdge Key;
+      typedef typename Map::Value Value;
+
+      ForwardComposeMap(const Graph& _graph, const Map& _map) 
+	: graph(_graph), map(_map) {}
+      
+      Value operator[](const Key& key) {
+	return map[graph.direct(key, false)];
+      }
+
+    private:
+      typename Ref<Map>::Type map;
+      const Graph& graph;
+    };
+
+    template <typename Graph, typename Map>
+    ForwardComposeMap<Graph, Map>
+    forwardComposeMap(const Graph& graph, const Map& map) {
+      return ForwardComposeMap<Graph, Map>(graph, map);
+    }
+
+    template <typename Graph, typename Map>
+    class BackwardComposeMap {
+    public:
+      typedef typename Graph::UndirEdge Key;
+      typedef typename Map::Value Value;
+
+      BackwardComposeMap(const Graph& _graph, const Map& _map) 
+	: graph(_graph), map(_map) {}
+      
+      Value operator[](const Key& key) {
+	return map[graph.direct(key, false)];
+      }
+
+    private:
+      typename Ref<Map>::Type map;
+      const Graph& graph;
+    };
+
+    template <typename Graph, typename Map>
+    BackwardComposeMap<Graph, Map>
+    backwardComposeMap(const Graph& graph, const Map& map) {
+      return BackwardComposeMap<Graph, Map>(graph, map);
+    }
+
+    template <typename Graph, typename Map>
+    struct Ref<ForwardComposeMap<Graph, Map> > { 
+      typedef ForwardComposeMap<Graph, Map> Type;
+    };
+
+    template <typename Graph, typename Map>
+    struct Ref<BackwardComposeMap<Graph, Map> > { 
+      typedef BackwardComposeMap<Graph, Map> Type; 
+    };
+
+    template <typename Map>
+    struct Ref<XMap<Map> > { 
+      typedef XMap<Map> Type;
+    };
+    template <typename Map>
+    struct Ref<ConstXMap<Map> > { 
+      typedef ConstXMap<Map> Type;
+    };
+
+    template <typename Map>
+    struct Ref<YMap<Map> > { 
+      typedef YMap<Map> Type;
+    };
+    template <typename Map>
+    struct Ref<ConstYMap<Map> > { 
+      typedef ConstYMap<Map> Type;
+    };
+
   }
 
   /// \ingroup io_group
@@ -234,7 +314,7 @@
       typedef typename Writer::Value Value;
       typedef _Item Item;
       
-      typename SmartConstReference<Map>::Type map;
+      typename _writer_bits::Ref<Map>::Type map;
       Writer writer;
 
       MapWriter(const Map& _map, const Writer& _writer) 
@@ -453,7 +533,7 @@
     WriterBase<Node>* idMap;
     bool forceIdMap;
    
-    typename SmartConstReference<Graph>::Type graph;   
+    const Graph& graph;   
     std::string id;
 
   };
@@ -627,7 +707,7 @@
     WriterBase<Edge>* idMap;
     bool forceIdMap;
    
-    typename SmartConstReference<Graph>::Type graph;   
+    const Graph& graph;   
     std::string id;
 
     std::auto_ptr<IdWriterBase<Node> > nodeIdWriter;
@@ -746,8 +826,10 @@
 				     const Writer& writer = Writer()) {
       checkConcept<concept::ReadMap<Edge, typename Map::Value>, Map>();
       checkConcept<_writer_bits::ItemWriter<typename Map::Value>, Writer>();
-      writeUndirEdge("+" + name, composeMap(forwardMap(graph), map), writer);
-      writeUndirEdge("-" + name, composeMap(backwardMap(graph), map), writer);
+      writeUndirEdge("+" + name, 
+		     _writer_bits::forwardComposeMap(graph, map), writer);
+      writeUndirEdge("-" + name, 
+		     _writer_bits::backwardComposeMap(graph, map), writer);
       return *this;
     }
 
@@ -853,7 +935,7 @@
     WriterBase<UndirEdge>* idMap;
     bool forceIdMap;
    
-    typename SmartConstReference<Graph>::Type graph;   
+    const Graph& graph;   
     std::string id;
 
     std::auto_ptr<IdWriterBase<Node> > nodeIdWriter;