diff -r 71dc900ee30f -r 882790531532 src/demo/tight_edge_filter_map.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/demo/tight_edge_filter_map.h	Thu Sep 30 16:08:20 2004 +0000
@@ -0,0 +1,63 @@
+/* -*- C++ -*-
+ * src/lemon/tight_edge_filter_map.h - Part of LEMON, a generic C++ optimization library
+ *
+ * Copyright (C) 2004 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
+ * (Egervary Combinatorial Optimization Research Group, EGRES).
+ *
+ * Permission to use, modify and distribute this software is granted
+ * provided that this copyright notice appears in all copies. For
+ * precise terms see the accompanying LICENSE file.
+ *
+ * This software is provided "AS IS" with no warranty of any kind,
+ * express or implied, and with no claim as to its suitability for any
+ * purpose.
+ *
+ */
+
+#ifndef LEMON_TIGHT_EDGE_FILTER_MAP_H
+#define LEMON_TIGHT_EDGE_FILTER_MAP_H
+
+#include <lemon/maps.h>
+
+// /// \file
+// /// \brief Maximum flow algorithms.
+// /// \ingroup galgs
+
+namespace lemon {
+
+  /// \brief A map for filtering the edge-set to those edges 
+  /// which are tight w.r.t. some node_potential map and 
+  /// edge_distance map.
+  ///
+  /// A node-map node_potential is said to be a potential w.r.t. 
+  /// an edge-map edge_distance 
+  /// if and only if for each edge e, node_potential[g.head(e)] 
+  /// <= edge_distance[e]+node_potential[g.tail(e)] 
+  /// (or the reverse inequality holds for each edge).
+  /// An edge is said to be tight if this inequality holds with equality, 
+  /// and the map returns true exactly for those edges.
+  /// To avoid rounding errors, it is recommended to use this class with exact 
+  /// types, e.g. with int.
+  template<typename Graph, 
+	   typename NodePotentialMap, typename EdgeDistanceMap>
+  class TightEdgeFilterMap : public MapBase<typename Graph::Edge, bool> {
+  protected:
+    const Graph* g;
+    NodePotentialMap* node_potential;
+    EdgeDistanceMap* edge_distance;
+  public:
+    TightEdgeFilterMap(Graph& _g, NodePotentialMap& _node_potential, 
+		       EdgeDistanceMap& _edge_distance) : 
+      g(&_g), node_potential(&_node_potential), 
+      edge_distance(&_edge_distance) { }
+    bool operator[](const typename Graph::Edge& e) const {
+      return ((*node_potential)[g->head(e)] == 
+	      (*edge_distance)[e]+(*node_potential)[g->tail(e)]);
+    }
+  };
+
+} //namespace lemon
+
+#endif //LEMON_TIGHT_EDGE_FILTER_MAP_H
+
+