From 15929ddde9cbe519415cce659ee4183f44673665 Mon Sep 17 00:00:00 2001
From: Ron Wein <wein@post.tau.ac.il>
Date: Thu, 3 Aug 2006 11:23:23 +0000
Subject: [PATCH] Added a default merge functor for the generic curve-data
 traits.

---
 .../examples/Arrangement_2/ex_dual_with_data.cpp     | 12 ++----------
 Arrangement_2/include/CGAL/Arr_curve_data_traits_2.h |  3 ++-
 .../include/CGAL/Arr_traits_2/Curve_data_aux.h       | 12 ++++++++++++
 3 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/Arrangement_2/examples/Arrangement_2/ex_dual_with_data.cpp b/Arrangement_2/examples/Arrangement_2/ex_dual_with_data.cpp
index f79885bdda7..b0ffe5b7566 100644
--- a/Arrangement_2/examples/Arrangement_2/ex_dual_with_data.cpp
+++ b/Arrangement_2/examples/Arrangement_2/ex_dual_with_data.cpp
@@ -8,20 +8,12 @@
 #include <CGAL/Arr_curve_data_traits_2.h>
 #include <CGAL/Arrangement_2.h>
 
-struct Default_merge
-{
-  unsigned int operator() (unsigned int, unsigned int) const
-  {
-    return (0);
-  }
-};
-
 typedef CGAL::Cartesian<Number_type>                     Kernel;
 typedef CGAL::Arr_linear_traits_2<Kernel>                Linear_traits_2;
 typedef Linear_traits_2::Point_2                         Point_2;
 typedef Linear_traits_2::Line_2                          Line_2;
-typedef CGAL::Arr_curve_data_traits_2
-          <Linear_traits_2, unsigned int, Default_merge> Traits_2; 
+typedef CGAL::Arr_curve_data_traits_2<Linear_traits_2,
+                                      unsigned int>      Traits_2; 
 typedef Traits_2::X_monotone_curve_2                     X_monotone_curve_2;
 typedef CGAL::Arrangement_2<Traits_2>                    Arrangement_2;
 
diff --git a/Arrangement_2/include/CGAL/Arr_curve_data_traits_2.h b/Arrangement_2/include/CGAL/Arr_curve_data_traits_2.h
index 91afb930849..192897109e8 100644
--- a/Arrangement_2/include/CGAL/Arr_curve_data_traits_2.h
+++ b/Arrangement_2/include/CGAL/Arr_curve_data_traits_2.h
@@ -41,7 +41,8 @@ CGAL_BEGIN_NAMESPACE
  * the overlapping subcurve is obtained from the merge functor.
  * All other functors are inherited from the base ordinary traits class.
  */
-template <class Traits_, class XMonotoneCurveData_, class Merge_,
+template <class Traits_, class XMonotoneCurveData_, 
+          class Merge_ = _Default_merge_func<XMonotoneCurveData_>,
           class CurveData_ = XMonotoneCurveData_,
           class Convert_ = _Default_convert_func<CurveData_,
                                                  XMonotoneCurveData_> >
diff --git a/Arrangement_2/include/CGAL/Arr_traits_2/Curve_data_aux.h b/Arrangement_2/include/CGAL/Arr_traits_2/Curve_data_aux.h
index 1ce0fce2128..01257378b4e 100644
--- a/Arrangement_2/include/CGAL/Arr_traits_2/Curve_data_aux.h
+++ b/Arrangement_2/include/CGAL/Arr_traits_2/Curve_data_aux.h
@@ -27,6 +27,18 @@
 
 CGAL_BEGIN_NAMESPACE
 
+/*!
+ * \struct A simple merge functor.
+ */
+template <class TYPE>
+struct _Default_merge_func
+{
+  const TYPE& operator() (const TYPE& obj1, const TYPE& obj2)
+  {
+    return (obj1);
+  }
+};
+
 /*!
  * \struct A simple convertor from one type to another.
  */