From c97223b933677b58fa12ffb80c6cabafeb241df0 Mon Sep 17 00:00:00 2001
From: Andreas Fabri <andreas.fabri@geometryfactory.com>
Date: Fri, 31 Mar 2017 11:20:47 +0200
Subject: [PATCH] Add an example for a triangulation hierarchy of a constrained
 Delaunay triangulation plus

---
 BGL/doc/BGL/examples.txt                      |   1 +
 .../emst_cdt_plus_hierarchy.cpp               | 112 ++++++++++++++++++
 2 files changed, 113 insertions(+)
 create mode 100644 BGL/examples/BGL_triangulation_2/emst_cdt_plus_hierarchy.cpp

diff --git a/BGL/doc/BGL/examples.txt b/BGL/doc/BGL/examples.txt
index f5260c52f1a..8eca963b8ab 100644
--- a/BGL/doc/BGL/examples.txt
+++ b/BGL/doc/BGL/examples.txt
@@ -12,6 +12,7 @@
 \example BGL_triangulation_2/dijkstra.cpp
 \example BGL_triangulation_2/dijkstra_with_internal_properties.cpp
 \example BGL_triangulation_2/emst.cpp
+\example BGL_triangulation_2/emst/emst_cdt_plus_hierarchy.cpp
 \example BGL_surface_mesh/prim.cpp
 \example BGL_surface_mesh/surface_mesh_dual.cpp
 \example Surface_mesh_skeletonization/simple_mcfskel_example.cpp
diff --git a/BGL/examples/BGL_triangulation_2/emst_cdt_plus_hierarchy.cpp b/BGL/examples/BGL_triangulation_2/emst_cdt_plus_hierarchy.cpp
new file mode 100644
index 00000000000..acac3a76a68
--- /dev/null
+++ b/BGL/examples/BGL_triangulation_2/emst_cdt_plus_hierarchy.cpp
@@ -0,0 +1,112 @@
+#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
+#include <CGAL/Delaunay_triangulation_2.h>
+#include <CGAL/Constrained_Delaunay_triangulation_2.h>
+#include <CGAL/Triangulation_hierarchy_2.h>
+#include <CGAL/Constrained_triangulation_plus_2.h>
+#include <CGAL/boost/graph/graph_traits_Delaunay_triangulation_2.h>
+#include <CGAL/boost/graph/graph_traits_Constrained_Delaunay_triangulation_2.h>
+#include <CGAL/boost/graph/graph_traits_Constrained_triangulation_plus_2.h>
+#include <CGAL/boost/graph/graph_traits_Triangulation_hierarchy_2.h>
+
+#include <boost/graph/kruskal_min_spanning_tree.hpp>
+#include <boost/graph/filtered_graph.hpp>
+#include <fstream>
+
+typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
+typedef K::Point_2 Point;
+
+typedef CGAL::Triangulation_vertex_base_2<K>             Vbb;
+typedef CGAL::Triangulation_hierarchy_vertex_base_2<Vbb> Vb;
+typedef CGAL::Constrained_triangulation_face_base_2<K>   Fb;
+typedef CGAL::Triangulation_data_structure_2<Vb,Fb>      TDS;
+typedef CGAL::Exact_predicates_tag                       Itag;
+typedef CGAL::Constrained_Delaunay_triangulation_2<K,TDS,Itag> CDT;
+typedef CGAL::Triangulation_hierarchy_2<CDT>             CDTH;
+typedef CGAL::Constrained_triangulation_plus_2<CDTH>     Triangulation;
+
+
+// As we only consider finite vertices and edges
+// we need the following filter
+
+template <typename T>
+struct Is_finite {
+
+  const T* t_;
+
+  Is_finite()
+    : t_(NULL)
+  {}
+
+  Is_finite(const T& t)
+    : t_(&t)
+  { }
+
+  template <typename VertexOrEdge>
+  bool operator()(const VertexOrEdge& voe) const {
+    return ! t_->is_infinite(voe);
+  }
+};
+
+typedef Is_finite<Triangulation> Filter;
+typedef boost::filtered_graph<Triangulation,Filter,Filter> Finite_triangulation;
+typedef boost::graph_traits<Finite_triangulation>::vertex_descriptor vertex_descriptor;
+typedef boost::graph_traits<Finite_triangulation>::vertex_iterator vertex_iterator;
+typedef boost::graph_traits<Finite_triangulation>::edge_descriptor edge_descriptor;
+
+// The BGL makes use of indices associated to the vertices
+// We use a std::map to store the index
+typedef std::map<vertex_descriptor,int> VertexIndexMap;
+VertexIndexMap vertex_id_map;
+
+// A std::map is not a property map, because it is not lightweight
+typedef boost::associative_property_map<VertexIndexMap> VertexIdPropertyMap;
+VertexIdPropertyMap vertex_index_pmap(vertex_id_map);
+
+int
+main(int argc,char* argv[])
+{
+  const char* filename = (argc > 1) ? argv[1] : "data/points.xy";
+  std::ifstream input(filename);
+  Triangulation t;
+  Filter is_finite(t);
+  Finite_triangulation ft(t, is_finite, is_finite);
+
+  Point p ;
+  while(input >> p){
+    t.insert(p);
+  }
+
+  vertex_iterator vit, ve;
+  // Associate indices to the vertices
+  int index = 0;
+  // boost::tie assigns the first and second element of the std::pair
+  // returned by boost::vertices to the variables vit and ve
+  for(boost::tie(vit,ve)=boost::vertices(ft); vit!=ve; ++vit ){
+    vertex_descriptor  vd = *vit;
+    vertex_id_map[vd]= index++;
+    }
+
+
+  // We use the default edge weight which is the squared length of the edge
+  // This property map is defined in graph_traits_Triangulation_2.h
+
+  // In the function call you can see a named parameter: vertex_index_map
+   std::list<edge_descriptor> mst;
+   boost::kruskal_minimum_spanning_tree(ft,
+					std::back_inserter(mst),
+					vertex_index_map(vertex_index_pmap));
+
+
+   std::cout << "The edges of the Euclidean mimimum spanning tree:" << std::endl;
+
+   for(std::list<edge_descriptor>::iterator it = mst.begin(); it != mst.end(); ++it){
+     edge_descriptor ed = *it;
+     vertex_descriptor svd = source(ed,t);
+     vertex_descriptor tvd = target(ed,t);
+     Triangulation::Vertex_handle sv = svd;
+     Triangulation::Vertex_handle tv = tvd;
+     std::cout << "[ " << sv->point() << "  |  " << tv->point() << " ] " << std::endl;
+   }
+
+   return 0;
+}