diff --git a/GPA_2/include/CGAL/GPA_2.h b/GPA_2/include/CGAL/GPA_2.h
index d55813d0710..c5d8003f15c 100755
--- a/GPA_2/include/CGAL/GPA_2.h
+++ b/GPA_2/include/CGAL/GPA_2.h
@@ -12,19 +12,18 @@
 //
 // ============================================================================
 
+#ifndef CGAL_GPA_2_H
+#define CGAL_GPA_2_H
+
 /*! \file GPA_2.h
  *  \brief defines class \c GPA_2
  *  
  *  General Points and Segments
  */
 
-#ifndef CGAL_GPA_2_H
-#define CGAL_GPA_2_H
-
 #include <CGAL/basic.h>
 #include <CGAL/GPA_2/Point_2.h>
 #include <CGAL/GPA_2/Arc_2.h>
-
 #include <CGAL/GPA_2/GPA_2_functors.h>
 
 CGAL_BEGIN_NAMESPACE
@@ -32,12 +31,12 @@ CGAL_BEGIN_NAMESPACE
 template < class CurveKernel_2 >
 class GPA_2 {
 
-// declares GPA functors and for each functor defines a member function
+// declares GPA functors, for each functor defines a member function
 // returning an instance of this functor
-#define CGAL_GPA_pred(Y,Z) \
+#define CGAL_GPA_pred(Y, Z) \
     typedef GPA_2_Functors::Y<Self> Y; \
-    Y Z() const { return Y(); }
-#define CGAL_GPA_cons(Y,Z) CGAL_GPA_pred(Y,Z)
+    Y Z() const { return Y(this); }
+#define CGAL_GPA_cons(Y, Z) CGAL_GPA_pred(Y, Z)
 
 public:
     //! \name public typedefs
@@ -71,24 +70,35 @@ public:
     typedef CGAL::Tag_true Has_merge_category; 
     //! tag specifies that infinite functors supported
     typedef CGAL::Tag_true Has_infinite_category;
-    //! tag specifies that unbounded arcs are supported
+    //! tag specifies that unbounded arcs supported
     typedef CGAL::Tag_true Has_boundary_category;
     
     //!@}
 public:
+    //! \name Constructors
+    //@{
+
+    //! default constructor
+    GPA_2() :
+        _m_kernel(Curve_kernel_2()) {
+    }
+
+    //! constructor uses specific \c Curve_kernel_2 instance (for controlling)
+    GPA_2(const Curve_kernel_2& kernel) :
+        _m_kernel(kernel) {
+    }
+    //!@}
     //!\name embedded types and predicates for \c Arrangement_2 package
     //!@{
-    
+        
     //! type of a point on generic curve
-    // or shall we alias Xy_coordinate_2 as a "finite" point to be used by
-    // ArrangementTraits_2, while Point_2 is only for internal purposes ?
     typedef CGALi::Point_2<Self> Point_2; 
     
     //! type of an arc on generic curve
     typedef CGALi::Arc_2<Self> Arc_2; 
     
     //! type of weakly x-monotone arc for \c ArrangementTraits_2
-    typedef Arc_2 X_monotone_curve;
+    typedef Arc_2 X_monotone_curve_2;
 
     CGAL_GPA_pred(Compare_x_2, compare_x_2_object)  + 
     CGAL_GPA_pred(Compare_xy_2, compare_xy_2_object)  +
@@ -96,8 +106,6 @@ public:
     CGAL_GPA_pred(Is_vertical_2, is_vertical_2_object) +
     CGAL_GPA_cons(Construct_min_vertex_2, construct_min_vertex_2_object) +
     CGAL_GPA_cons(Construct_max_vertex_2, construct_max_vertex_2_object) +
-    CGAL_GPA_pred(Infinite_in_x_2, infinite_in_x_2_object) + ?
-    CGAL_GPA_pred(Infinite_in_y_2, infinite_in_y_2_object) + ?
     CGAL_GPA_pred(Boundary_in_x_2, boundary_in_x_2_object) +
     CGAL_GPA_pred(Boundary_in_y_2, boundary_in_y_2_object) +
     CGAL_GPA_pred(Compare_y_at_x_2, compare_y_at_x_2_object) +  
@@ -111,13 +119,28 @@ public:
     CGAL_GPA_pred(Are_mergeable_2, are_mergeable_2_object) +
     CGAL_GPA_cons(Merge_2, merge_2_object) +
     CGAL_GPA_pred(Do_overlap_2, do_overlap_2_object); +
-    CGAL_GPA_cons(Trim_2, trim_2_object);
+    CGAL_GPA_cons(Trim_2, trim_2_object); +
     CGAL_GPA_pred(Is_in_x_range_2, is_in_x_range_2_object); +
     
     /*CGAL_GPA_cons(Approximate_2, approximate_2_object)
     CGAL_GPA_cons(Construct_x_monotone_curve_2,
         construct_x_monotone_curve_2_object)*/
         
+     //! returns internal \c Curve_kernel_2 instance
+    Curve_kernel_2 kernel() const {
+        return _m_kernel;
+    }
+    
+#under CGAL_GPA_pred
+#under CGAL_GPA_cons    
+
+    //!@}
+private:
+    //!@{
+    //!\name private members
+    
+    Curve_kernel_2 _m_kernel;
+    
     //!@}
 }; // class GPA_2