CGAL::Cartesian_converter< K1, K2, NTConverter > Class Template Reference

#include <CGAL/Cartesian_converter.h>

Definition

Cartesian_converter converts objects from the kernel traits K1 to the kernel traits K2 using NTConverter to do the conversion.

Those traits must be of the form Cartesian<FT1> and Cartesian<FT2> (or the equivalent with Simple_cartesian). It then provides the following operators to convert objects from K1 to K2.

The third template parameter NTConverter is a function object that must provide K2::FT operator()(K1::FT n) that converts n to an K2::FT which has the same value.

The default value of this parameter is CGAL::NT_converter<K1::FT, K2::FT>.

Example

In the following example, we compute exactly the intersection point between a line and a triangle, and we then create a double approximation of this point.

File Kernel_23/cartesian_converter.cpp

#include <CGAL/Simple_cartesian.h>
#include <CGAL/Quotient.h>
#include <CGAL/MP_Float.h>
#include <CGAL/Cartesian_converter.h>

typedef CGAL::Simple_cartesian<double>                           IK;
typedef CGAL::Simple_cartesian<CGAL::Quotient<CGAL::MP_Float> >  EK;
typedef CGAL::Cartesian_converter<IK,EK>                         IK_to_EK;
typedef CGAL::Cartesian_converter<EK,IK>                         EK_to_IK;

int main(){
  IK::Triangle_3 t1(
    IK::Point_3(0.,0.,0.),
    IK::Point_3(1.,0.,-1.),
    IK::Point_3(0.,1.,3.)
  );
  
  IK::Line_3 l1(
    IK::Point_3(0.2,0.25,-7),
    IK::Point_3(0.25,0.3,4)
  );
  
  IK_to_EK to_exact;
  
  EK::Triangle_3 t2=to_exact(t1);
  EK::Line_3     l2=to_exact(l1);
  
  CGAL::cpp11::result_of<EK::Intersect_3(EK::Triangle_3, EK::Line_3)>::type
    inter = CGAL::intersection(t2,l2);

  // As we are sure that there IS an intersection
  // and that the intersection IS a point 
  // we do not have to check for this, or put it in a try/catch
  const EK::Point_3& exact_pt = boost::get<EK::Point_3>(*inter);
  
  EK_to_IK to_inexact;
  
  IK::Point_3 inexact_pt = to_inexact(exact_pt);
  std::cout << inexact_pt << std::endl;
  return 0;
}

See Also

CGAL::Cartesian<FieldNumberType>

CGAL::Simple_cartesian<FieldNumberType>

Examples:

Filtered_kernel/Filtered_predicate.cpp, and Kernel_23/cartesian_converter.cpp.

Creation
	Cartesian_converter ()
	Default constructor.

Operations
Similar operators are defined for the other kernel traits types Point_3, Vector_2...
K2::Point_2	operator() (const K1::Point_2 &p)
	returns a K2::Point_2 which coordinates are those of p, converted by NTConverter.