Merge pull request #2108 from sloriot/CH2-add_missing_requirement

Document a missing requirement in 2D convex hull traits concept

(This merge also merge releases/CGAL-4.10-branch, so that `master` stays
ahead of it.)

Convex_hull_2/doc/Convex_hull_2/CGAL/convex_hull_traits_2.h

@@ -58,6 +58,11 @@ typedef R::Left_turn_2 Left_turn_2;
 */ 
 typedef R::Equal_2 Equal_2; 
 
+/*!
+
+*/
+typedef R::Orientation_2 Orientation_2;
+
 /// @} 
 
 /// \name Creation 
@@ -104,6 +109,11 @@ Left_turn_2 left_turn_2_object();
 */ 
 Equal_2 equal_2_object(); 
 
+/*!
+
+*/
+Orientation_2 orientation_2_object();
+
 /// @}
 
 }; /* end Convex_hull_traits_2 */

Convex_hull_2/doc/Convex_hull_2/Concepts/ConvexHullTraits_2.h

@@ -89,6 +89,15 @@ is smaller!
 */ 
 typedef unspecified_type Less_rotate_ccw_2; 
 
+/*!
+Predicate object type that must provide
+`Orientation operator()(Point_2 e, Point_2 p,Point_2 q)`,
+that returns `CGAL::LEFT_TURN`, if `r` lies to the left of the oriented line `l`
+defined by `p` and `q`, returns `CGAL::RIGHT_TURN` if `r` lies to the right of `l`,
+and returns `CGAL::COLLINEAR` if `r` lies on `l`.
+*/
+typedef unspecified_type Orientation_2;
+
 /// @} 
 
 /// \name Creation 
@@ -137,6 +146,11 @@ Less_rotate_ccw_2 less_rotate_ccw_2_object( );
 */ 
 Left_turn_2 left_turn_2_object(); 
 
+/*!
+
+*/
+Orientation_2 orientation_2_object();
+
 /// @}
 
 }; /* end ConvexHullTraits_2 */

Convex_hull_2/test/Convex_hull_2/ch2_point_with_info.cpp

@@ -0,0 +1,133 @@
+#include <iostream>
+#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
+#include <CGAL/convex_hull_2.h>
+#include <CGAL/convex_hull_traits_2.h>
+#include <boost/iterator/counting_iterator.hpp>
+
+#include <boost/foreach.hpp>
+
+typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
+typedef K::Point_2 Point_2;
+
+
+template <class F, class Point>
+struct Forward_bool_functor
+  : public F
+{
+  const std::vector<Point>& points;
+
+  Forward_bool_functor(const std::vector<Point>& points)
+    : points(points)
+  {}
+
+  template <class Id>
+  bool operator() (const Id& p, const Id& q) const
+  {
+    return static_cast<const F*>(this)->operator()(points[p], points[q]);
+  }
+
+  template <class Id>
+  bool operator() (const Id& p, const Id& q, const Id& r) const
+  {
+    return static_cast<const F*>(this)->operator()(points[p], points[q], points[r]);
+  }
+
+  template <class Id>
+  bool operator() (const Id& p, const Id& q, const Id& r, const Id& s) const
+  {
+    return static_cast<const F*>(this)->operator()(points[p], points[q], points[r], points[s]);
+  }
+};
+
+template <class K>
+struct CH_traits_for_point_ids
+{
+  const std::vector<typename K::Point_2>& points;
+
+  CH_traits_for_point_ids(const std::vector<typename K::Point_2>& points)
+    : points(points)
+  {}
+
+  typedef std::size_t Point_2;
+  typedef CGAL::Convex_hull_traits_2<K> Base;
+  typedef Forward_bool_functor<typename Base::Less_xy_2, typename K::Point_2> Less_xy_2;
+  typedef Forward_bool_functor<typename Base::Less_yx_2, typename K::Point_2> Less_yx_2;
+  typedef Forward_bool_functor<typename Base::Less_signed_distance_to_line_2, typename K::Point_2> Less_signed_distance_to_line_2;
+  typedef Forward_bool_functor<typename Base::Less_rotate_ccw_2, typename K::Point_2> Less_rotate_ccw_2;
+  typedef Forward_bool_functor<typename Base::Left_turn_2, typename K::Point_2> Left_turn_2;
+  typedef Forward_bool_functor<typename Base::Equal_2, typename K::Point_2> Equal_2;
+
+  struct Orientation_2
+  {
+    const std::vector<typename K::Point_2>& points;
+
+    Orientation_2(const std::vector<typename K::Point_2>& points)
+      : points(points)
+    {}
+
+    CGAL::Orientation
+    operator()(Point_2 p, Point_2 q, Point_2 r) const
+    {
+      return typename Base::Orientation_2()(points[p], points[q], points[r]);
+    }
+  };
+
+  Equal_2 equal_2_object () const
+  {
+    return Equal_2(points);
+  }
+
+  Less_xy_2 less_xy_2_object () const
+  {
+    return Less_xy_2(points);
+  }
+
+  Less_yx_2 less_yx_2_object () const
+  {
+    return Less_yx_2(points);
+  }
+
+  Less_signed_distance_to_line_2 less_signed_distance_to_line_2_object () const
+  {
+    return Less_signed_distance_to_line_2(points);
+  }
+
+  Less_rotate_ccw_2 less_rotate_ccw_2_object () const
+  {
+    return Less_rotate_ccw_2(points);
+  }
+
+  Left_turn_2 left_turn_2_object () const
+  {
+    return Left_turn_2(points);
+  }
+
+  Orientation_2 orientation_2_object () const
+  {
+    return Orientation_2(points);
+  }
+};
+
+int main()
+{
+  std::vector<Point_2> input_points;
+  std::vector<std::size_t> result;
+
+  input_points.push_back( Point_2(0,0) );
+  input_points.push_back( Point_2(0,1) );
+  input_points.push_back( Point_2(1,0) );
+  input_points.push_back( Point_2(0.25,0.25) );
+
+  CGAL::convex_hull_2( boost::counting_iterator<std::size_t>(0),
+                       boost::counting_iterator<std::size_t>(input_points.size()),
+                       std::back_inserter(result), CH_traits_for_point_ids<K>(input_points) );
+
+  BOOST_FOREACH(std::size_t i, result)
+  {
+    std::cout << input_points[i] << " - " << i << "\n";
+  }
+
+  assert( result.size() == 3 );
+
+  return 0;
+}