diff -r d8475431bbbb -r 8e85e6bbefdf demo/tight_edge_filter_map.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/demo/tight_edge_filter_map.h	Mon May 23 04:48:14 2005 +0000
@@ -0,0 +1,68 @@
+/* -*- C++ -*-
+ * demo/tight_edge_filter_map.h - Part of LEMON, a generic C++ optimization
+ * library
+ *
+ * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
+ * (Egervary Research Group on Combinatorial Optimization, 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. a node-potential and 
+    edge-distance.
+    
+    Let \f$G=(V,A)\f$ be a directed graph (graph for short) and 
+    let \f$\mathbb{F}\f$ be a number type. 
+    Given a distance function 
+    \f$d:E\to\mathbb{F}\f$, 
+    \f$\pi:V\to\mathbb{F}\f$ is said to be a potetial 
+    w.r.t. \f$d\f$ 
+    if and only if 
+    \f$\pi(v)\le d(uv)+\pi(u)\f$ holds for each edge \f$uv\in E\f$ 
+    (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 \c true exactly for those edges. 
+    To avoid rounding errors, it is recommended to use this class with exact 
+    number types, e.g. with \c 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->target(e)] == 
+	      (*edge_distance)[e]+(*node_potential)[g->source(e)]);
+    }
+  };
+
+} //namespace lemon
+
+#endif //LEMON_TIGHT_EDGE_FILTER_MAP_H