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+/*    This file is part of the Gudhi Library. The Gudhi library 
+ *    (Geometric Understanding in Higher Dimensions) is a generic C++ 
+ *    library for computational topology.
+ *
+ *    Author(s):       Clément Maria
+ *
+ *    Copyright (C) 2014  INRIA Sophia Antipolis-Méditerranée (France)
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the GNU General Public License as published by
+ *    the Free Software Foundation, either version 3 of the License, or
+ *    (at your option) any later version.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU General Public License for more details.
+ *
+ *    You should have received a copy of the GNU General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef GRAPH_SIMPLICIAL_COMPLEX_H_
+#define GRAPH_SIMPLICIAL_COMPLEX_H_
+
+#include <boost/graph/adjacency_list.hpp>
+
+#include <utility>  // for pair<>
+#include <vector>
+#include <map>
+
+/* Edge tag for Boost PropertyGraph. */
+struct edge_filtration_t {
+  typedef boost::edge_property_tag kind;
+};
+
+/* Vertex tag for Boost PropertyGraph. */
+struct vertex_filtration_t {
+  typedef boost::vertex_property_tag kind;
+};
+
+typedef int Vertex_handle;
+typedef double Filtration_value;
+typedef boost::adjacency_list < boost::vecS, boost::vecS, boost::undirectedS
+, boost::property < vertex_filtration_t, Filtration_value >
+, boost::property < edge_filtration_t, Filtration_value >
+> Graph_t;
+typedef std::pair< Vertex_handle, Vertex_handle > Edge_t;
+
+/** \brief Output the proximity graph of the points.
+ *
+ * If points contains n elements, the proximity graph is the graph 
+ * with n vertices, and an edge [u,v] iff the distance function between 
+ * points u and v is smaller than threshold.
+ *
+ * The type PointCloud furnishes .begin() and .end() methods, that return
+ * iterators with value_type Point.
+ */
+template< typename PointCloud
+, typename Point >
+Graph_t compute_proximity_graph(PointCloud &points
+                                , Filtration_value threshold
+                                , Filtration_value distance(Point p1, Point p2)) {
+  std::vector< Edge_t > edges;
+  std::vector< Filtration_value > edges_fil;
+  std::map< Vertex_handle, Filtration_value > vertices;
+
+  Vertex_handle idx_u, idx_v;
+  Filtration_value fil;
+  idx_u = 0;
+  for (auto it_u = points.begin(); it_u != points.end(); ++it_u) {
+    idx_v = idx_u + 1;
+    for (auto it_v = it_u + 1; it_v != points.end(); ++it_v, ++idx_v) {
+      fil = distance(*it_u, *it_v);
+      if (fil <= threshold) {
+        edges.emplace_back(idx_u, idx_v);
+        edges_fil.push_back(fil);
+      }
+    }
+    ++idx_u;
+  }
+
+  Graph_t skel_graph(edges.begin()
+                     , edges.end()
+                     , edges_fil.begin()
+                     , idx_u);  // number of points labeled from 0 to idx_u-1
+
+  auto vertex_prop = boost::get(vertex_filtration_t(), skel_graph);
+
+  boost::graph_traits<Graph_t>::vertex_iterator vi, vi_end;
+  for (std::tie(vi, vi_end) = boost::vertices(skel_graph);
+       vi != vi_end; ++vi) {
+    boost::put(vertex_prop, *vi, 0.);
+  }
+
+  return skel_graph;
+}
+
+#endif  // GRAPH_SIMPLICIAL_COMPLEX_H_