CGAL users discussion list

[Kai WANG <>]

You are right Sebastien...Even if A added the "sqrt", there are still erros showing the "atan" "sin" "cos" need to be re-defined...
Does it mean I need to use two kinds of kernels in a same project if I want to ensure the calculation of intersection and linear_least_square_fitting at the same time?

On Thu, Oct 6, 2011 at 11:49 PM, Sebastien Loriot (GeometryFactory) <> wrote:

You cannot do it exactly. You can only get an approximation.

Something like this should work

K::FT sqrt(K::FT v) {
 return K::FT(std::sqrt(CGAL::to_double(v)));
}

No guarantee that you will not have a problem with another
function not available for this number type.

Sebastien.


Kai WANG wrote:

I'm sorry that I still don't quite understand how to modify it. Could you please give a detailed explanation on the way to add a "sqrt" function please? For example, given the following simple program which has complile error, where should I add the "sqrt" function please?
Thanks very much for ur help!


typedef CGAL::Exact_predicates_exact_constructions_kernel K;
typedef K::Line_3            Line;
typedef K::Plane_3           Plane;
typedef K::Point_3           Point;
typedef K::Triangle_3        Triangle;

int main(void)
{
 std::list<Triangle> triangles;
 Point a(1.0,2.0,3.0);
 Point b(4.0,0.0,6.0);
 Point c(7.0,8.0,9.0);
 Point d(8.0,7.0,6.0);
 Point e(5.0,3.0,4.0);
 triangles.push_back(Triangle(a,b,c));
 triangles.push_back(Triangle(a,b,d));
 triangles.push_back(Triangle(d,e,c));

 Line line;
 Plane plane;

 // fit plane to whole triangles
 linear_least_squares_fitting_3(triangles.begin(),triangles.end(),plane,CGAL::Dimension_tag<2>());
  // fit line to triangle vertices
 linear_least_squares_fitting_3(triangles.begin(),triangles.end(),line, CGAL::Dimension_tag<0>());
  return 0;
}

On Thu, Oct 6, 2011 at 11:31 PM, Sebastien Loriot (GeometryFactory) < <mailto:>> wrote:

   the PCA package make use of the square root function, so the underlying
   number type in the kernel you are using should have a sqrt function
   available.

   Sebastien.



   kyewong wrote:

       Hi,
       When I'm using the linear_least_squares_fitting_3 and

       CGAL::Exact_predicates_exact___constructions_kernel as kernel,

       there will be a
       compile error as follows.
       Could anyone tell me how to modify it if I want to use both of
       them at the
       same time please? Thanks very much!

       1>F:\Program Files\CGAL-3.8\include\CGAL/__PCA_util.h(132) :

       error C2665:
       'sqrt' : none of the 3 overloads could convert all the argument
       types
       1>        F:\Program Files\Microsoft Visual Studio
       9.0\VC\include\math.h(581): could be 'long double sqrt(long double)'
       1>        F:\Program Files\Microsoft Visual Studio
       9.0\VC\include\math.h(533): or       'float sqrt(float)'
       1>        F:\Program Files\Microsoft Visual Studio
       9.0\VC\include\math.h(128): or       'double sqrt(double)'
       1>        while trying to match the argument list
       '(CGAL::Lazy_exact_nt<ET_>)'
       1>        with
       1>        [
       1>            ET_=CGAL::Gmpq
       1>        ]
       1>        F:\Program

       Files\CGAL-3.8\include\CGAL/__linear_least_squares_fitting___triangles_3.h(57)

       :
       see reference to function template instantiation 'void

       CGAL::internal::assemble___covariance_matrix_3&lt;__InputIterator,K&gt;(__InputIterator,InputIterator,__CGAL::Lazy_exact_nt<ET_>

       [],const CGAL::Point_3<R_> &,const K &,const
       CGAL::Triangle_3<R_> *,const
       CGAL::Dimension_tag<dim> &)' being compiled
       1>        with
       1>        [

       1>            InputIterator=std::list<__Triangle>::_Iterator<true>,

       1>            K=CGAL::Epeck,
       1>            ET_=CGAL::Gmpq,
       1>            R_=CGAL::Epeck,
       1>            dim=2
       1>        ]
       1>        F:\Program

       Files\CGAL-3.8\include\CGAL/__linear_least_squares_fitting___3.h(58)

       : see
       reference to function template instantiation
       'CGAL::Lazy_exact_nt<ET_>

       CGAL::internal::linear_least___squares_fitting_3&lt;__InputIterator,Kernel&gt;(__InputIterator,InputIterator,__CGAL::Plane_3<R_>

       &,CGAL::Point_3<R_> &,const CGAL::Triangle_3<R_> *,const K &,const
       CGAL::Dimension_tag<dim> &)' being compiled
       1>        with
       1>        [
       1>            ET_=CGAL::Gmpq,

       1>            InputIterator=std::list<__Triangle>::_Iterator<true>,

       1>            Kernel=CGAL::Epeck,
       1>            R_=CGAL::Epeck,
       1>            K=CGAL::Epeck,
       1>            dim=2
       1>        ]
       1>        F:\Program

       Files\CGAL-3.8\include\CGAL/__linear_least_squares_fitting___3.h(76)

       : see
       reference to function template instantiation
       'CGAL::Lazy_exact_nt<ET_>

       CGAL::linear_least_squares___fitting_3&lt;InputIterator,__Object,CGAL::Epeck,Tag&gt;(__InputIterator,InputIterator,__Object

       &,CGAL::Point_3<R_> &,const Tag &,const Kernel &)' being compiled
       1>        with
       1>        [
       1>            ET_=CGAL::Gmpq,

       1>            InputIterator=std::list<__Triangle>::_Iterator<true>,

       1>            Object=Plane,
       1>            Tag=CGAL::Dimension_tag<2>,
       1>            R_=CGAL::Epeck,
       1>            Kernel=CGAL::Epeck
       1>        ]
       1>        F:\Program

       Files\CGAL-3.8\include\CGAL/__linear_least_squares_fitting___3.h(93)

       : see
       reference to function template instantiation
       'CGAL::Lazy_exact_nt<ET_>

       CGAL::linear_least_squares___fitting_3&lt;InputIterator,__Object,CGAL::Point_3&lt;R_&gt;__,Tag>(InputIterator,__InputIterator,Object

       &,Point &,const Tag &)' being compiled
       1>        with
       1>        [
       1>            ET_=CGAL::Gmpq,

       1>            InputIterator=std::list<__Triangle>::_Iterator<true>,

       1>            Object=Plane,
       1>            R_=CGAL::Epeck,
       1>            Tag=CGAL::Dimension_tag<2>,

       1>            Point=CGAL::Point_3<CGAL::__Epeck>
       1>        ]
       1>        .\linear_least_squares___fitting_triangles_3.cpp(33) :

       see reference
       to function template instantiation 'CGAL::Lazy_exact_nt<ET_>

       CGAL::linear_least_squares___fitting_3&lt;std::list&lt;_Ty&__gt;::_Iterator<_Secure___validation>,Plane,CGAL::__Dimension_tag<dim>>(__InputIterator,InputIterator,__Object

       &,const Tag &)' being compiled
       1>        with
       1>        [
       1>            ET_=CGAL::Gmpq,
       1>            _Ty=Triangle,
       1>            _Secure_validation=true,
       1>            dim=2,

       1>            InputIterator=std::list<__Triangle>::_Iterator<true>,

       1>            Object=Plane,
       1>            Tag=CGAL::Dimension_tag<2>
       1>        ]

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       <http://cgal-discuss.949826.n4.nabble.com/compiling-error-of-linear-least-squares-fitting-3-under-Exact-predicates-exact-constructions-kernel-tp3878596p3878596.html>
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Kai WANG

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