// Copyright (c) 2008 Max-Planck-Institute Saarbruecken (Germany).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org)
//
// $URL: https://github.com/CGAL/cgal/blob/v6.1/Polynomial/include/CGAL/Polynomial_traits_d.h $
// $Id: include/CGAL/Polynomial_traits_d.h b26b07a1242 $
// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s)     : Michael Hemmer <hemmer@informatik.uni-mainz.de>
//                 Sebastian Limbach <slimbach@mpi-inf.mpg.de>
//
// ============================================================================
#ifndef CGAL_POLYNOMIAL_TRAITS_D_H
#define CGAL_POLYNOMIAL_TRAITS_D_H

#include <CGAL/disable_warnings.h>

#include <CGAL/basic.h>
#include <functional>
#include <list>
#include <vector>
#include <utility>

#include <CGAL/Polynomial/fwd.h>
#include <CGAL/Polynomial/misc.h>
#include <CGAL/Polynomial/Polynomial_type.h>
#include <CGAL/Polynomial/Monomial_representation.h>
#include <CGAL/Polynomial/Degree.h>
#include <CGAL/polynomial_utils.h>
#include <CGAL/Polynomial/square_free_factorize.h>
#include <CGAL/Polynomial/modular_filter.h>
#include <CGAL/extended_euclidean_algorithm.h>
#include <CGAL/Polynomial/resultant.h>
#include <CGAL/Polynomial/subresultants.h>
#include <CGAL/Polynomial/sturm_habicht_sequence.h>

#include <CGAL/boost/iterator/transform_iterator.hpp>
#include <CGAL/tss.h>


#define CGAL_POLYNOMIAL_TRAITS_D_BASE_TYPEDEFS                          \
  private:                                                              \
  typedef Polynomial_traits_d< Polynomial< Coefficient_type_ > > PT;    \
  typedef Polynomial_traits_d< Coefficient_type_ > PTC;                 \
                                                                        \
  typedef Polynomial<Coefficient_type_>               Polynomial_d;     \
  typedef Coefficient_type_                          Coefficient_type;  \
                                                                        \
  typedef typename Innermost_coefficient_type<Polynomial_d>::Type       \
  Innermost_coefficient_type;                                           \
  static const int d = Dimension<Polynomial_d>::value;                  \
                                                                        \
                                                                        \
  typedef std::pair< Exponent_vector, Innermost_coefficient_type >      \
  Exponents_coeff_pair;                                                 \
  typedef std::vector< Exponents_coeff_pair > Monom_rep;                \
                                                                        \
  typedef CGAL::Recursive_const_flattening< d-1,                        \
    typename CGAL::Polynomial<Coefficient_type>::const_iterator >       \
  Coefficient_const_flattening;                                         \
                                                                        \
  typedef typename                                                      \
  Coefficient_const_flattening::Recursive_flattening_iterator           \
  Innermost_coefficient_const_iterator;                                 \
                                                                        \
  typedef typename  Polynomial_d::const_iterator                        \
  Coefficient_const_iterator;                                           \
                                                                        \
  typedef std::pair<Innermost_coefficient_const_iterator,               \
                    Innermost_coefficient_const_iterator>               \
  Innermost_coefficient_const_iterator_range;                           \
                                                                        \
  typedef std::pair<Coefficient_const_iterator,                         \
                    Coefficient_const_iterator>                         \
  Coefficient_const_iterator_range;                                     \



namespace CGAL {

namespace internal {

// Base class for functors depending on the algebraic category of the
// innermost coefficient
template< class Coefficient_type_, class ICoeffAlgebraicCategory >
class Polynomial_traits_d_base_icoeff_algebraic_category {
public:
  typedef Null_functor    Multivariate_content;
};

// Specializations
template< class Coefficient_type_ >
class Polynomial_traits_d_base_icoeff_algebraic_category<
            Polynomial< Coefficient_type_ >, Integral_domain_without_division_tag >
  : public Polynomial_traits_d_base_icoeff_algebraic_category<
                Polynomial< Coefficient_type_ >, Null_tag > {};

template< class Coefficient_type_ >
class Polynomial_traits_d_base_icoeff_algebraic_category<
       Polynomial< Coefficient_type_ >, Integral_domain_tag >
  : public Polynomial_traits_d_base_icoeff_algebraic_category<
       Polynomial< Coefficient_type_ >, Integral_domain_without_division_tag > {};

template< class Coefficient_type_ >
class Polynomial_traits_d_base_icoeff_algebraic_category<
            Polynomial< Coefficient_type_ >, Unique_factorization_domain_tag >
  : public Polynomial_traits_d_base_icoeff_algebraic_category<
                Polynomial< Coefficient_type_ >, Integral_domain_tag > {
  CGAL_POLYNOMIAL_TRAITS_D_BASE_TYPEDEFS

public:


 struct Multivariate_content
    : public CGAL::cpp98::unary_function< Polynomial_d , Innermost_coefficient_type >{
    Innermost_coefficient_type
    operator()(const Polynomial_d& p) const {
      typedef Innermost_coefficient_const_iterator IT;
      Innermost_coefficient_type content(0);
      typename PT::Construct_innermost_coefficient_const_iterator_range range;
      for (IT it = range(p).first; it != range(p).second; it++){
        content = CGAL::gcd(content, *it);
        if(CGAL::is_one(content)) break;
      }
      return content;
    }
  };
};

template< class Coefficient_type_ >
class Polynomial_traits_d_base_icoeff_algebraic_category<
            Polynomial< Coefficient_type_ >, Euclidean_ring_tag >
  : public Polynomial_traits_d_base_icoeff_algebraic_category<
                Polynomial< Coefficient_type_ >, Unique_factorization_domain_tag >
{};

template< class Coefficient_type_ >
class Polynomial_traits_d_base_icoeff_algebraic_category<
            Polynomial< Coefficient_type_ >, Field_tag >
  : public Polynomial_traits_d_base_icoeff_algebraic_category<
                Polynomial< Coefficient_type_ >, Integral_domain_tag > {
  CGAL_POLYNOMIAL_TRAITS_D_BASE_TYPEDEFS

public:

  //       Multivariate_content;
  struct Multivariate_content
    : public CGAL::cpp98::unary_function< Polynomial_d , Innermost_coefficient_type >{
    Innermost_coefficient_type operator()(const Polynomial_d& p) const {
      if( CGAL::is_zero(p) )
        return Innermost_coefficient_type(0);
      else
        return Innermost_coefficient_type(1);
    }
  };
};

template< class Coefficient_type_ >
class Polynomial_traits_d_base_icoeff_algebraic_category<
            Polynomial< Coefficient_type_ >, Field_with_sqrt_tag >
  : public Polynomial_traits_d_base_icoeff_algebraic_category<
                Polynomial< Coefficient_type_ >, Field_tag > {};

template< class Coefficient_type_ >
class Polynomial_traits_d_base_icoeff_algebraic_category<
            Polynomial< Coefficient_type_ >, Field_with_kth_root_tag >
  : public Polynomial_traits_d_base_icoeff_algebraic_category<
                Polynomial< Coefficient_type_ >, Field_with_sqrt_tag > {};

template< class Coefficient_type_ >
class Polynomial_traits_d_base_icoeff_algebraic_category<
            Polynomial< Coefficient_type_ >, Field_with_root_of_tag >
  : public Polynomial_traits_d_base_icoeff_algebraic_category<
                Polynomial< Coefficient_type_ >, Field_with_kth_root_tag > {};

// Base class for functors depending on the algebraic category of the
// Polynomial type
template< class Coefficient_type_, class PolynomialAlgebraicCategory >
class Polynomial_traits_d_base_polynomial_algebraic_category {
public:
  typedef Null_functor    Univariate_content;
  typedef Null_functor    Square_free_factorize;
};

// Specializations
template< class Coefficient_type_ >
class Polynomial_traits_d_base_polynomial_algebraic_category<
            Polynomial< Coefficient_type_ >, Integral_domain_without_division_tag >
  : public Polynomial_traits_d_base_polynomial_algebraic_category<
                Polynomial< Coefficient_type_ >, Null_tag > {};

template< class Coefficient_type_ >
class Polynomial_traits_d_base_polynomial_algebraic_category<
            Polynomial< Coefficient_type_ >, Integral_domain_tag >
  : public Polynomial_traits_d_base_polynomial_algebraic_category<
          Polynomial< Coefficient_type_ >, Integral_domain_without_division_tag > {};

template< class Coefficient_type_ >
class Polynomial_traits_d_base_polynomial_algebraic_category<
            Polynomial< Coefficient_type_ >, Unique_factorization_domain_tag >
  : public Polynomial_traits_d_base_polynomial_algebraic_category<
                Polynomial< Coefficient_type_ >, Integral_domain_tag > {
  CGAL_POLYNOMIAL_TRAITS_D_BASE_TYPEDEFS

public:

  //       Univariate_content
  struct Univariate_content
    : public CGAL::cpp98::unary_function< Polynomial_d , Coefficient_type>{
    Coefficient_type operator()(const Polynomial_d& p) const {
      return p.content();
    }
  };

  //       Square_free_factorize;
  struct Square_free_factorize{

    template < class OutputIterator >
    OutputIterator operator()( const Polynomial_d& p, OutputIterator oi) const {
      std::vector<Polynomial_d> factors;
      std::vector<int> mults;

      square_free_factorize
        ( p, std::back_inserter(factors), std::back_inserter(mults) );

      CGAL_postcondition( factors.size() == mults.size() );
      for(unsigned int i = 0; i < factors.size(); i++){
        *oi++=std::make_pair(factors[i],mults[i]);
      }

      return oi;
    }

    template< class OutputIterator >
    OutputIterator operator()(
        const Polynomial_d&    p ,
        OutputIterator         oi,
        Innermost_coefficient_type& a ) const {

      if( CGAL::is_zero(p) ) {
        a = Innermost_coefficient_type(0);
        return oi;
      }

      typedef Polynomial_traits_d< Polynomial_d > PT;
      typename PT::Innermost_leading_coefficient ilcoeff;
      typename PT::Multivariate_content mcontent;
      a = CGAL::unit_part( ilcoeff( p ) ) * mcontent( p );

      return (*this)( p/Polynomial_d(a), oi);
    }
  };
};

template< class Coefficient_type_ >
class Polynomial_traits_d_base_polynomial_algebraic_category<
            Polynomial< Coefficient_type_ >, Euclidean_ring_tag >
  : public Polynomial_traits_d_base_polynomial_algebraic_category<
                Polynomial< Coefficient_type_ >, Unique_factorization_domain_tag > {};


// Polynomial_traits_d_base class connecting the two base classes which depend
//  on the algebraic category of the innermost coefficient type and the poly-
//  nomial type.

// First the general base class for the innermost coefficient
template< class InnermostCoefficient_type,
          class ICoeffAlgebraicCategory, class PolynomialAlgebraicCategory >
class Polynomial_traits_d_base {
  typedef InnermostCoefficient_type ICoeff;
public:
  static const int d = 0;

  typedef ICoeff Polynomial_d;
  typedef ICoeff Coefficient_type;
  typedef ICoeff Innermost_coefficient_type;

  struct Degree
    : public CGAL::cpp98::unary_function< ICoeff , int > {
    int operator()(const ICoeff&) const { return 0; }
  };
  struct Total_degree
    : public CGAL::cpp98::unary_function< ICoeff , int > {
    int operator()(const ICoeff&) const { return 0; }
  };

  typedef Null_functor  Construct_polynomial;
  typedef Null_functor  Get_coefficient;
  typedef Null_functor  Leading_coefficient;
  typedef Null_functor  Univariate_content;
  typedef Null_functor  Multivariate_content;
  typedef Null_functor  Shift;
  typedef Null_functor  Negate;
  typedef Null_functor  Invert;
  typedef Null_functor  Translate;
  typedef Null_functor  Translate_homogeneous;
  typedef Null_functor  Scale_homogeneous;
  typedef Null_functor  Differentiate;

  struct Is_square_free
    : public CGAL::cpp98::unary_function< ICoeff, bool > {
    bool operator()( const ICoeff& ) const {
      return true;
    }
  };

  struct Make_square_free
    : public CGAL::cpp98::unary_function< ICoeff, ICoeff>{
    ICoeff operator()( const ICoeff& x ) const {
      if (CGAL::is_zero(x)) return x ;
      else  return ICoeff(1);
    }
  };

  typedef Null_functor  Square_free_factorize;
  typedef Null_functor  Pseudo_division;
  typedef Null_functor  Pseudo_division_remainder;
  typedef Null_functor  Pseudo_division_quotient;

  struct Gcd_up_to_constant_factor
    : public CGAL::cpp98::binary_function< ICoeff, ICoeff, ICoeff >{
    ICoeff operator()(const ICoeff& x, const ICoeff& y) const {
      if (CGAL::is_zero(x) && CGAL::is_zero(y))
        return ICoeff(0);
      else
        return ICoeff(1);
    }
  };

  typedef Null_functor Integral_division_up_to_constant_factor;

  struct Univariate_content_up_to_constant_factor
    : public CGAL::cpp98::unary_function< ICoeff, ICoeff >{
    ICoeff operator()(const ICoeff& ) const {
      // TODO: Why not return 0 if argument is 0 ?
      return ICoeff(1);
    }
  };

  typedef Null_functor  Square_free_factorize_up_to_constant_factor;
  typedef Null_functor  Resultant;
  typedef Null_functor  Canonicalize;
  typedef Null_functor  Evaluate_homogeneous;

  struct Innermost_leading_coefficient
    :public CGAL::cpp98::unary_function <ICoeff, ICoeff>{
    const ICoeff& operator()(const ICoeff& x){return x;}
  };

  struct Degree_vector{
    typedef Exponent_vector         result_type;
    typedef Coefficient_type             argument_type;
    // returns the exponent vector of inner_most_lcoeff.
    result_type operator()(const Coefficient_type&) const{
      return Exponent_vector();
    }
  };

  struct Get_innermost_coefficient
    : public CGAL::cpp98::binary_function< ICoeff, Polynomial_d, Exponent_vector > {
    const ICoeff& operator()( const Polynomial_d& p, Exponent_vector ) {
      return p;
    }
  };

  typedef Null_functor Evaluate ;

  struct Substitute{
  public:
    template <class Input_iterator>
    typename
    CGAL::Coercion_traits<
        typename std::iterator_traits<Input_iterator>::value_type,
                                   Innermost_coefficient_type>::Type
    operator()(
        const Innermost_coefficient_type& p,
        Input_iterator CGAL_precondition_code(begin),
        Input_iterator CGAL_precondition_code(end) ) const {
      CGAL_precondition(end == begin);
      typedef typename std::iterator_traits<Input_iterator>::value_type
        value_type;
      typedef CGAL::Coercion_traits<Innermost_coefficient_type,value_type> CT;
      return typename CT::Cast()(p);
    }
  };

  struct Substitute_homogeneous{
  public:
    // this is the end of the recursion
    // begin contains the homogeneous variable
    // hdegree is the remaining degree
    template <class Input_iterator>
    typename
    CGAL::Coercion_traits<
        typename std::iterator_traits<Input_iterator>::value_type,
                                   Innermost_coefficient_type>::Type
    operator()(
        const Innermost_coefficient_type& p,
        Input_iterator begin,
        Input_iterator CGAL_precondition_code(end),
        int hdegree) const {

      typedef typename std::iterator_traits<Input_iterator>::value_type
        value_type;
      typedef CGAL::Coercion_traits<Innermost_coefficient_type,value_type> CT;
      typename CT::Type result =
        typename CT::Cast()(CGAL::ipower(*begin++,hdegree))
        * typename CT::Cast()(p);

      CGAL_precondition(end == begin);
      CGAL_precondition(hdegree >= 0);
      return result;
    }
  };
};

// Now the version for the polynomials with all functors provided by all
// polynomials
template< class Coefficient_type_,
          class ICoeffAlgebraicCategory, class PolynomialAlgebraicCategory >
class Polynomial_traits_d_base< Polynomial< Coefficient_type_ >,
          ICoeffAlgebraicCategory, PolynomialAlgebraicCategory >
  : public Polynomial_traits_d_base_icoeff_algebraic_category<
        Polynomial< Coefficient_type_ >, ICoeffAlgebraicCategory >,
    public Polynomial_traits_d_base_polynomial_algebraic_category<
        Polynomial< Coefficient_type_ >, PolynomialAlgebraicCategory > {

  typedef Polynomial_traits_d< Polynomial< Coefficient_type_ > > PT;
  typedef Polynomial_traits_d< Coefficient_type_ > PTC;

  public:
  typedef Polynomial<Coefficient_type_>                  Polynomial_d;
  typedef Coefficient_type_                              Coefficient_type;

  typedef typename internal::Innermost_coefficient_type<Polynomial_d>::Type
  Innermost_coefficient_type;
  static const int d = Dimension<Polynomial_d>::value;

private:
  typedef std::pair< Exponent_vector, Innermost_coefficient_type >
  Exponents_coeff_pair;
  typedef std::vector< Exponents_coeff_pair > Monom_rep;

  typedef CGAL::Recursive_const_flattening< d-1,
    typename CGAL::Polynomial<Coefficient_type>::const_iterator >
  Coefficient_const_flattening;

  public:
  typedef typename Coefficient_const_flattening::Recursive_flattening_iterator
  Innermost_coefficient_const_iterator;
  typedef typename  Polynomial_d::const_iterator Coefficient_const_iterator;

  typedef std::pair<Innermost_coefficient_const_iterator,
                    Innermost_coefficient_const_iterator>
                    Innermost_coefficient_const_iterator_range;

  typedef std::pair<Coefficient_const_iterator,
                    Coefficient_const_iterator>
                    Coefficient_const_iterator_range;


  // We use our own Strict Weak Ordering predicate in order to avoid
  // problems when calling sort for an `Exponents_coeff_pair` where the
  // coeff type has no comparison operators available.
private:
  struct Compare_exponents_coeff_pair
    : public CGAL::cpp98::binary_function<
       std::pair< Exponent_vector, Innermost_coefficient_type >,
       std::pair< Exponent_vector, Innermost_coefficient_type >,
       bool >
  {
    bool operator()(
        const std::pair< Exponent_vector, Innermost_coefficient_type >& p1,
        const std::pair< Exponent_vector, Innermost_coefficient_type >& p2 ) const {
      // TODO: Precondition leads to an error within test_translate in
      // Polynomial_traits_d test
      // CGAL_precondition( p1.first != p2.first );
      return p1.first < p2.first;
    }
  };

public:

  //
  // Functors as defined in the reference manual
  // (with sometimes slightly extended functionality)

  // Construct_polynomial;
  struct Construct_polynomial {

    typedef Polynomial_d  result_type;

    Polynomial_d operator()()  const {
      return Polynomial_d(0);
    }

    template <class T>
    Polynomial_d operator()( T a ) const {
      return Polynomial_d(a);
    }

    //! construct the constant polynomial a0
    Polynomial_d operator() (const Coefficient_type& a0) const
    {return Polynomial_d(a0);}

    //! construct the polynomial a0 + a1*x
    Polynomial_d operator() (
        const Coefficient_type& a0, const Coefficient_type& a1) const
    {return Polynomial_d(a0,a1);}

    //! construct the polynomial a0 + a1*x + a2*x^2
    Polynomial_d operator() (
        const Coefficient_type& a0, const Coefficient_type& a1,
        const Coefficient_type& a2) const
    {return Polynomial_d(a0,a1,a2);}

    //! construct the polynomial a0 + a1*x + ... + a3*x^3
    Polynomial_d operator() (
        const Coefficient_type& a0, const Coefficient_type& a1,
        const Coefficient_type& a2, const Coefficient_type& a3) const
    {return Polynomial_d(a0,a1,a2,a3);}

    //! construct the polynomial a0 + a1*x + ... + a4*x^4
    Polynomial_d operator() (
        const Coefficient_type& a0, const Coefficient_type& a1,
        const Coefficient_type& a2, const Coefficient_type& a3,
        const Coefficient_type& a4) const
    {return Polynomial_d(a0,a1,a2,a3,a4);}

    //! construct the polynomial a0 + a1*x + ... + a5*x^5
    Polynomial_d operator() (
        const Coefficient_type& a0, const Coefficient_type& a1,
        const Coefficient_type& a2, const Coefficient_type& a3,
        const Coefficient_type& a4, const Coefficient_type& a5) const
    {return Polynomial_d(a0,a1,a2,a3,a4,a5);}

    //! construct the polynomial a0 + a1*x + ... + a6*x^6
    Polynomial_d operator() (
        const Coefficient_type& a0, const Coefficient_type& a1,
        const Coefficient_type& a2, const Coefficient_type& a3,
        const Coefficient_type& a4, const Coefficient_type& a5,
        const Coefficient_type& a6) const
    {return Polynomial_d(a0,a1,a2,a3,a4,a5,a6);}

    //! construct the polynomial a0 + a1*x + ... + a7*x^7
    Polynomial_d operator() (
        const Coefficient_type& a0, const Coefficient_type& a1,
        const Coefficient_type& a2, const Coefficient_type& a3,
        const Coefficient_type& a4, const Coefficient_type& a5,
        const Coefficient_type& a6, const Coefficient_type& a7) const
    {return Polynomial_d(a0,a1,a2,a3,a4,a5,a6,a7);}

    //! construct the polynomial a0 + a1*x + ... + a8*x^8
    Polynomial_d operator() (
        const Coefficient_type& a0, const Coefficient_type& a1,
        const Coefficient_type& a2, const Coefficient_type& a3,
        const Coefficient_type& a4, const Coefficient_type& a5,
        const Coefficient_type& a6, const Coefficient_type& a7,
        const Coefficient_type& a8) const
    {return Polynomial_d(a0,a1,a2,a3,a4,a5,a6,a7,a8);}

#if 1
  private:
    template <class Input_iterator, class NT> Polynomial_d
    construct_value_type(Input_iterator begin, Input_iterator end, NT) const {
      typedef CGAL::Coercion_traits<NT,Coefficient_type> CT;
      static_assert(std::is_same<typename CT::Type,Coefficient_type>::value);
      typename CT::Cast cast;
      return Polynomial_d(
          boost::make_transform_iterator(begin,cast),
          boost::make_transform_iterator(end,cast));
    }

    template <class Input_iterator, class NT> Polynomial_d
    construct_value_type(Input_iterator begin, Input_iterator end, std::pair<Exponent_vector,NT>) const {
      return (*this)(begin,end,false);// construct from non sorted monom rep
    }

  public:
    template< class Input_iterator >
    Polynomial_d operator()( Input_iterator begin, Input_iterator end) const {
      if(begin == end ) return Polynomial_d(0);
      typedef typename std::iterator_traits<Input_iterator>::value_type value_type;
      return construct_value_type(begin,end,value_type());
    }

    template< class Input_iterator >
    Polynomial_d operator()( Input_iterator begin, Input_iterator end, bool is_sorted) const {
      // Avoid compiler warning
      (void)is_sorted;
      if(begin == end ) return Polynomial_d(0);
      Monom_rep monom_rep(begin,end);
      // if(!is_sorted)
      std::sort(monom_rep.begin(),monom_rep.end(),Compare_exponents_coeff_pair());
      return Create_polynomial_from_monom_rep<Coefficient_type>()(monom_rep.begin(),monom_rep.end());
    }
#else

    // Construct from Coefficient type
    template< class Input_iterator >
    inline Polynomial_d
    construct( Input_iterator begin, Input_iterator end, Tag_true) const {
      if(begin == end ) return Polynomial_d(0);
      return Polynomial_d(begin,end);
    }
    // Construct from momom rep
    template< class Input_iterator >
    inline Polynomial_d
    construct( Input_iterator begin, Input_iterator end, Tag_false) const {
      // construct from non sorted monom rep
      return (*this)(begin,end,false);
    }

    template< class Input_iterator >
    Polynomial_d
    operator()( Input_iterator begin, Input_iterator end ) const {
      if(begin == end ) return Polynomial_d(0);
      typedef typename std::iterator_traits<Input_iterator>::value_type value_type;
      typedef Boolean_tag<std::is_same<value_type,Coefficient_type>::value>
        Is_coeff;
      std::vector<value_type> vec(begin,end);
      return construct(vec.begin(),vec.end(),Is_coeff());
    }


    template< class Input_iterator >
    Polynomial_d
    operator()(Input_iterator begin, Input_iterator end , bool is_sorted) const{
      if(!is_sorted)
        std::sort(begin,end,Compare_exponents_coeff_pair());
      return Create_polynomial_from_monom_rep< Coefficient_type >()(begin,end);
    }
#endif

  public:

    template< class T >
    class Create_polynomial_from_monom_rep {
    public:
      template <class Monom_rep_iterator>
      Polynomial_d operator()(
          Monom_rep_iterator begin,
          Monom_rep_iterator end) const {

        Innermost_coefficient_type zero(0);
        std::vector< Innermost_coefficient_type > coefficients;
        for(Monom_rep_iterator it = begin; it != end; it++){
          int current_exp = it->first[0];
          if((int) coefficients.size() < current_exp)
            coefficients.resize(current_exp,zero);
          coefficients.push_back(it->second);
        }
        return Polynomial_d(coefficients.begin(),coefficients.end());
      }
    };

    template< class T >
    class Create_polynomial_from_monom_rep< Polynomial < T > > {
    public:
      template <class Monom_rep_iterator>
      Polynomial_d operator()(
          Monom_rep_iterator begin,
          Monom_rep_iterator end) const {

        typedef Polynomial_traits_d<Coefficient_type> PT;
        typename PT::Construct_polynomial construct;

        static_assert(PT::d != 0); // Coefficient_type is a Polynomial
        std::vector<Coefficient_type> coefficients;

        Coefficient_type zero(0);
        while(begin != end){
          int current_exp = begin->first[PT::d];
          // fill up with zeros until current exp is reached
          if((int) coefficients.size() < current_exp)
            coefficients.resize(current_exp,zero);

          // select range for coefficient of current exponent
          Monom_rep_iterator coeff_end = begin;
          while(  coeff_end != end && coeff_end->first[PT::d] == current_exp ){
            ++coeff_end;
          }
          coefficients.push_back(construct(begin, coeff_end));
          begin = coeff_end;
        }
        return Polynomial_d(coefficients.begin(),coefficients.end());
      }
    };
  };

  // Get_coefficient;
  struct Get_coefficient
    : public CGAL::cpp98::binary_function<Polynomial_d, int, Coefficient_type > {

    const Coefficient_type& operator()( const Polynomial_d& p, int i) const {
      CGAL_STATIC_THREAD_LOCAL_VARIABLE(Coefficient_type, zero, 0);
      CGAL_precondition( i >= 0 );
      typename PT::Degree degree;
      if( i >  degree(p) )
        return zero;
      return p[i];
    }
  };

  //     Get_innermost_coefficient;
  struct Get_innermost_coefficient
    : public CGAL::cpp98::binary_function< Polynomial_d,
                                           Exponent_vector,
                                           Innermost_coefficient_type >
  {

    const Innermost_coefficient_type&
    operator()( const Polynomial_d& p, Exponent_vector ev ) const {
      CGAL_precondition( !ev.empty() );
      typename PTC::Get_innermost_coefficient gic;
      typename PT::Get_coefficient gc;
      int exponent = ev.back();
      ev.pop_back();
      return gic( gc( p, exponent ), ev );
    };
  };

  typedef CGAL::internal::Monomial_representation<Polynomial_d> Monomial_representation;

  // Swap variable x_i with x_j
  struct Swap {
    typedef Polynomial_d        result_type;
    typedef Polynomial_d        first_argument_type;
    typedef int                 second_argument_type;
    typedef int                 third_argument_type;

  public:

    Polynomial_d operator()(const Polynomial_d& p, int i, int j ) const {
      CGAL_precondition(0 <= i && i < d);
      CGAL_precondition(0 <= j && j < d);
      typedef std::pair< Exponent_vector, Innermost_coefficient_type >
        Exponents_coeff_pair;
      Monomial_representation gmr;
      Construct_polynomial construct;
      typedef std::vector< Exponents_coeff_pair > Monom_vector;
      typedef typename Monom_vector::iterator MVIterator;
      Monom_vector monoms;
      gmr( p, std::back_inserter( monoms ) );
      for( MVIterator it = monoms.begin(); it != monoms.end(); ++it ) {
        std::swap(it->first[i],it->first[j]);
      }
      // sort only once !
      std::sort(monoms.begin(), monoms.end(),Compare_exponents_coeff_pair());
      return construct(monoms.begin(), monoms.end(),true);
    }
  };


  //       Move;
  // move variable x_i to position of x_j
  // order of other variables remains
  // default j = d makes x_i the othermost variable
  struct Move {
    typedef Polynomial_d        result_type;
    typedef Polynomial_d        first_argument_type;
    typedef int                 second_argument_type;
    typedef int                 third_argument_type;

    Polynomial_d
    operator()(const Polynomial_d& p, int i, int j = (d-1) ) const {
      CGAL_precondition(0 <= i && i < d);
      CGAL_precondition(0 <= j && j < d);
      typedef std::pair< Exponent_vector, Innermost_coefficient_type >
        Exponents_coeff_pair;
      typedef std::vector< Exponents_coeff_pair > Monom_rep;
      Monomial_representation gmr;
      Construct_polynomial construct;
      Monom_rep mon_rep;
      gmr( p, std::back_inserter( mon_rep ) );
      for( typename Monom_rep::iterator it = mon_rep.begin();
           it != mon_rep.end();
           ++it ) {
        // this is as good as std::rotate since it uses swap also
        if (i < j)
          for( int k = i; k < j; k++ )
            std::swap(it->first[k],it->first[k+1]);
        else
          for( int k = i; k > j; k-- )
            std::swap(it->first[k],it->first[k-1]);

      }
      return construct( mon_rep.begin(), mon_rep.end() );
    }
  };


  struct Permute {
    typedef Polynomial_d        result_type;
    template <typename Input_iterator> Polynomial_d operator()
      (const Polynomial_d& p, Input_iterator first, Input_iterator last) const {
      Construct_polynomial construct;
      Monomial_representation gmr;
      Monom_rep mon_rep;
      gmr( p, std::back_inserter( mon_rep ));
      std::vector<int> on_place, number_is;
      int i= 0;
      for (Input_iterator  iter = first ; iter != last ; ++iter)
        number_is.push_back (i++);
      on_place = number_is;
      int rem_place = 0, rem_number = i= 0;
      for(Input_iterator iter = first ; iter != last ; ++iter){
        for( typename Monom_rep::iterator it = mon_rep.begin();  it !=
               mon_rep.end(); ++it )
          std::swap(it->first[number_is[i]],it->first[(*iter)]);


        rem_place= number_is[i];
        rem_number= on_place[(*iter)];

        on_place[(*iter)] = i;
        on_place[rem_place]=rem_number;
        number_is[rem_number]=rem_place;
        number_is[i++]= (*iter);
      }
      return construct( mon_rep.begin(), mon_rep.end() );
    }
  };

  //Degree;
  typedef CGAL::internal::Degree<Polynomial_d> Degree;

  //       Total_degree;
  struct Total_degree : public CGAL::cpp98::unary_function< Polynomial_d , int >{
    int operator()(const Polynomial_d& p) const {
      typedef Polynomial_traits_d<Coefficient_type> COEFF_POLY_TRAITS;
      typename COEFF_POLY_TRAITS::Total_degree total_degree;
      Degree degree;
      CGAL_precondition( degree(p) >= 0);

      int result = 0;
      for(int i = 0; i <= degree(p) ; i++){
        if( ! CGAL::is_zero( p[i]) )
          result = (std::max)(result , total_degree(p[i]) + i );
      }
      return result;
    }
  };

  //       Leading_coefficient;
  struct Leading_coefficient
    : public CGAL::cpp98::unary_function< Polynomial_d , Coefficient_type>{
    const Coefficient_type& operator()(const Polynomial_d& p) const {
      return p.lcoeff();
    }
  };

  //       Innermost_leading_coefficient;
  struct Innermost_leading_coefficient
    : public CGAL::cpp98::unary_function< Polynomial_d , Innermost_coefficient_type>{
    const Innermost_coefficient_type&
    operator()(const Polynomial_d& p) const {
      typename PTC::Innermost_leading_coefficient ilcoeff;
      typename PT::Leading_coefficient lcoeff;
      return ilcoeff(lcoeff(p));
    }
  };


  //return a canonical representative of all constant multiples.
  struct Canonicalize
    : public CGAL::cpp98::unary_function<Polynomial_d, Polynomial_d>{

  private:
    inline Polynomial_d canonicalize_(Polynomial_d p, CGAL::Tag_true) const
    {
      typedef typename Polynomial_traits_d<Polynomial_d>::Innermost_coefficient_type IC;
      typename Polynomial_traits_d<Polynomial_d>::Innermost_leading_coefficient ilcoeff;
      typename Algebraic_extension_traits<IC>::Normalization_factor nfac;

      IC tmp = nfac(ilcoeff(p));
      if(tmp != IC(1)){
        p *= Polynomial_d(tmp);
      }
      remove_scalar_factor(p);
      p /= p.unit_part();
      p.simplify_coefficients();

      CGAL_postcondition(nfac(ilcoeff(p)) == IC(1));
      return p;
    };

    inline Polynomial_d canonicalize_(Polynomial_d p, CGAL::Tag_false) const
    {
      remove_scalar_factor(p);
      p /= p.unit_part();
      p.simplify_coefficients();
      return p;
    };

  public:
    Polynomial_d
    operator()( const Polynomial_d& p ) const {
      if (CGAL::is_zero(p)) return p;

      typedef Innermost_coefficient_type IC;
      typedef typename Algebraic_extension_traits<IC>::Is_extended Is_extended;
      return canonicalize_(p, Is_extended());
    }
  };

  //       Differentiate;
  struct Differentiate
    : public CGAL::cpp98::unary_function<Polynomial_d, Polynomial_d>{
    Polynomial_d
    operator()(Polynomial_d p, int i = (d-1)) const {
      if (i == (d-1) ){
        p.diff();
      }else{
        Swap swap;
        p = swap(p,i,d-1);
        p.diff();
        p = swap(p,i,d-1);
      }
      return p;
    }
  };

  // Evaluate;
  struct Evaluate
    :public CGAL::cpp98::binary_function<Polynomial_d,Coefficient_type,Coefficient_type>{
    // Evaluate with respect to one variable
    Coefficient_type
    operator()(const Polynomial_d& p, const Coefficient_type& x) const {
      return p.evaluate(x);
    }
#define ICOEFF typename First_if_different<Innermost_coefficient_type, Coefficient_type>::Type
    Coefficient_type operator()
      ( const Polynomial_d& p, const ICOEFF& x) const
    {
      return p.evaluate(x);
    }
#undef ICOEFF
  };

  // Evaluate_homogeneous;
  struct Evaluate_homogeneous{
    typedef Coefficient_type           result_type;
    typedef Polynomial_d               first_argument_type;
    typedef Coefficient_type           second_argument_type;
    typedef Coefficient_type           third_argument_type;

    Coefficient_type operator()(
        const Polynomial_d& p, const Coefficient_type& a, const Coefficient_type& b) const
    {
      return p.evaluate_homogeneous(a,b);
    }
#define ICOEFF typename First_if_different<Innermost_coefficient_type, Coefficient_type>::Type
    Coefficient_type operator()
      ( const Polynomial_d& p, const ICOEFF& a, const ICOEFF& b) const
    {
      return p.evaluate_homogeneous(a,b);
    }
#undef ICOEFF

  };

  // Is_zero_at;
  struct Is_zero_at {
  private:
    typedef Algebraic_structure_traits<Innermost_coefficient_type> AST;
    typedef typename AST::Is_zero::result_type BOOL;
  public:
    typedef BOOL result_type;

    template< class Input_iterator >
    BOOL operator()(
        const Polynomial_d& p,
        Input_iterator begin,
        Input_iterator end ) const {
      typename PT::Substitute substitute;
      return( CGAL::is_zero( substitute( p, begin, end ) ) );
    }
  };

  //  Is_zero_at_homogeneous;
  struct Is_zero_at_homogeneous {
 private:
    typedef Algebraic_structure_traits<Innermost_coefficient_type> AST;
    typedef typename AST::Is_zero::result_type BOOL;
  public:
    typedef BOOL result_type;

    template< class Input_iterator >
    BOOL operator()
      ( const Polynomial_d& p, Input_iterator begin, Input_iterator end ) const
    {
      typename PT::Substitute_homogeneous substitute_homogeneous;
      return( CGAL::is_zero( substitute_homogeneous( p, begin, end ) ) );
    }
  };

  // Sign_at, Sign_at_homogeneous, Compare
  // define XXX_ even though ICoeff may not be Real_embeddable
  // select proper XXX among XXX_ or Null_functor using ::std::conditional_t
private:
  struct Sign_at_ {
  private:
    typedef Real_embeddable_traits<Innermost_coefficient_type> RT;
  public:
    typedef typename RT::Sign result_type;

    template< class Input_iterator >
    result_type operator()(
        const Polynomial_d& p,
        Input_iterator begin,
        Input_iterator end ) const
    {
      typename PT::Substitute substitute;
      return CGAL::sign( substitute( p, begin, end ) );
    }
  };

  struct Sign_at_homogeneous_ {
    typedef Real_embeddable_traits<Innermost_coefficient_type> RT;
  public:
    typedef typename RT::Sign result_type;

    template< class Input_iterator >
    result_type operator()(
        const Polynomial_d& p,
        Input_iterator begin,
        Input_iterator end) const {
      typename PT::Substitute_homogeneous substitute_homogeneous;
      return CGAL::sign( substitute_homogeneous( p, begin, end ) );
    }
  };

  typedef Real_embeddable_traits<Innermost_coefficient_type> RET_IC;
  typedef typename RET_IC::Is_real_embeddable IC_is_real_embeddable;
public:
  typedef std::conditional_t<IC_is_real_embeddable::value,Sign_at_,Null_functor> Sign_at;
  typedef std::conditional_t<IC_is_real_embeddable::value,Sign_at_homogeneous_,Null_functor> Sign_at_homogeneous;
  typedef typename Real_embeddable_traits<Polynomial_d>::Compare Compare;


struct Construct_coefficient_const_iterator_range
     : public CGAL::cpp98::unary_function< Polynomial_d,
                                  Coefficient_const_iterator_range> {
    Coefficient_const_iterator_range
    operator () (const Polynomial_d& p) const {
      return std::make_pair( p.begin(), p.end() );
    }
};

struct Construct_innermost_coefficient_const_iterator_range
   : public CGAL::cpp98::unary_function< Polynomial_d,
                                 Innermost_coefficient_const_iterator_range> {
   Innermost_coefficient_const_iterator_range
   operator () (const Polynomial_d& p) const {
     return std::make_pair(
         typename Coefficient_const_flattening::Flatten()(p.end(),p.begin()),
         typename Coefficient_const_flattening::Flatten()(p.end(),p.end()));
   }
};

  struct Is_square_free
    : public CGAL::cpp98::unary_function< Polynomial_d, bool >{
    bool operator()( const Polynomial_d& p ) const {
      if( !internal::may_have_multiple_factor( p ) )
        return true;

      Gcd_up_to_constant_factor gcd_utcf;
      Univariate_content_up_to_constant_factor ucontent_utcf;
      Integral_division_up_to_constant_factor  idiv_utcf;
      Differentiate diff;

      Coefficient_type content = ucontent_utcf( p );
      typename PTC::Is_square_free isf;

      if( !isf( content ) )
        return false;

      Polynomial_d regular_part = idiv_utcf( p, Polynomial_d( content ) );

      Polynomial_d g = gcd_utcf(regular_part,diff(regular_part));
      return ( g.degree() == 0 );
    }
  };


  struct Make_square_free
    : public CGAL::cpp98::unary_function< Polynomial_d, Polynomial_d >{
    Polynomial_d
    operator()(const Polynomial_d& p) const {
      if (CGAL::is_zero(p)) return p;
      Gcd_up_to_constant_factor gcd_utcf;
      Univariate_content_up_to_constant_factor ucontent_utcf;
      Integral_division_up_to_constant_factor  idiv_utcf;
      Differentiate diff;
      typename PTC::Make_square_free msf;

      Coefficient_type content = ucontent_utcf(p);
      Polynomial_d result = Polynomial_d(msf(content));

      Polynomial_d regular_part = idiv_utcf(p,Polynomial_d(content));
      Polynomial_d g = gcd_utcf(regular_part,diff(regular_part));


      result *= idiv_utcf(regular_part,g);
      return Canonicalize()(result);

    }
  };

  //       Pseudo_division;
  struct Pseudo_division {
    typedef Polynomial_d        result_type;
    void
    operator()(
        const Polynomial_d& f, const Polynomial_d& g,
        Polynomial_d& q, Polynomial_d& r, Coefficient_type& D) const {
      Polynomial_d::pseudo_division(f,g,q,r,D);
    }
  };

  struct Pseudo_division_quotient
    :public CGAL::cpp98::binary_function<Polynomial_d, Polynomial_d, Polynomial_d> {

    Polynomial_d
    operator()(const Polynomial_d& f, const Polynomial_d& g) const {
      Polynomial_d q,r;
      Coefficient_type D;
      Polynomial_d::pseudo_division(f,g,q,r,D);
      return q;
    }
  };

  struct Pseudo_division_remainder
    :public CGAL::cpp98::binary_function<Polynomial_d, Polynomial_d, Polynomial_d> {

    Polynomial_d
    operator()(const Polynomial_d& f, const Polynomial_d& g) const {
      Polynomial_d q,r;
      Coefficient_type D;
      Polynomial_d::pseudo_division(f,g,q,r,D);
      return r;
    }
  };

  struct Gcd_up_to_constant_factor
    :public CGAL::cpp98::binary_function<Polynomial_d, Polynomial_d, Polynomial_d> {
    Polynomial_d
    operator()(const Polynomial_d& p, const Polynomial_d& q) const {
      if(p==q) return CGAL::canonicalize(p);
      if (CGAL::is_zero(p) && CGAL::is_zero(q)){
        return Polynomial_d(0);
      }
      // apply modular filter first
      if (internal::may_have_common_factor(p,q)){
        return internal::gcd_utcf_(p,q);
      }else{
        return Polynomial_d(1);
      }
    }
  };

  struct Integral_division_up_to_constant_factor
    :public CGAL::cpp98::binary_function<Polynomial_d, Polynomial_d, Polynomial_d> {



    Polynomial_d
    operator()(const Polynomial_d& p, const Polynomial_d& q) const {
      typedef Innermost_coefficient_type IC;

      typename PT::Construct_polynomial construct;
      typename PT::Innermost_leading_coefficient ilcoeff;
      typename PT::Construct_innermost_coefficient_const_iterator_range range;
      typedef Algebraic_extension_traits<Innermost_coefficient_type> AET;
      typename AET::Denominator_for_algebraic_integers dfai;
      typename AET::Normalization_factor nfac;


      IC ilcoeff_q = ilcoeff(q);
      // this factor is needed in case IC is an Algebraic extension
      IC dfai_q = dfai(range(q).first, range(q).second);
      // make dfai_q a 'scalar'
      ilcoeff_q *= dfai_q * nfac(dfai_q);

      Polynomial_d result = (p * construct(ilcoeff_q)) / q;

      return Canonicalize()(result);
    }
  };

  struct Univariate_content_up_to_constant_factor
    :public CGAL::cpp98::unary_function<Polynomial_d, Coefficient_type> {
    Coefficient_type
    operator()(const Polynomial_d& p) const {
      typename PTC::Gcd_up_to_constant_factor gcd_utcf;

      if(CGAL::is_zero(p)) return Coefficient_type(0);
      if(PT::d == 1) return Coefficient_type(1);

      Coefficient_type result(0);
      for(typename Polynomial_d::const_iterator it = p.begin();
          it != p.end();
          it++){
        result = gcd_utcf(*it,result);
      }
      return result;

    }
  };

  struct Square_free_factorize_up_to_constant_factor {
  private:
    typedef Coefficient_type Coeff;
    typedef Innermost_coefficient_type ICoeff;

    // rsqff_utcf computes the sqff recursively for Coeff
    // end of recursion: ICoeff

    template < class OutputIterator >
    OutputIterator rsqff_utcf ( ICoeff , OutputIterator oi) const{
      return oi;
    }

    template < class OutputIterator >
    OutputIterator rsqff_utcf (
        typename First_if_different<Coeff,ICoeff>::Type c,
        OutputIterator                                 oi) const {

      typename PTC::Square_free_factorize_up_to_constant_factor sqff;
      std::vector<std::pair<Coefficient_type,int> > fac_mul_pairs;
      sqff(c,std::back_inserter(fac_mul_pairs));

      for(unsigned int i = 0; i < fac_mul_pairs.size(); i++){
        Polynomial_d factor(fac_mul_pairs[i].first);
        int mult = fac_mul_pairs[i].second;
        *oi++=std::make_pair(factor,mult);
      }
      return oi;
    }

  public:
    template < class OutputIterator>
    OutputIterator
    operator()(Polynomial_d p, OutputIterator oi) const {
      if (CGAL::is_zero(p)) return oi;

      Univariate_content_up_to_constant_factor ucontent_utcf;
      Integral_division_up_to_constant_factor idiv_utcf;
      Coefficient_type c = ucontent_utcf(p);

      p = idiv_utcf( p , Polynomial_d(c));
      std::vector<Polynomial_d> factors;
      std::vector<int> mults;
      square_free_factorize_utcf(
          p, std::back_inserter(factors), std::back_inserter(mults));
      for(unsigned int i = 0; i < factors.size() ; i++){
         *oi++=std::make_pair(factors[i],mults[i]);
      }
      if (CGAL::total_degree(c) == 0)
        return oi;
      else
        return rsqff_utcf(c,oi);
    }
  };

  struct Shift
    : public CGAL::cpp98::binary_function< Polynomial_d,int,Polynomial_d >{

    Polynomial_d
    operator()(const Polynomial_d& p, int e, int i = (d-1)) const {
      Construct_polynomial construct;
      Monomial_representation gmr;
      Monom_rep monom_rep;
      gmr(p,std::back_inserter(monom_rep));
      for(typename Monom_rep::iterator it = monom_rep.begin();
          it != monom_rep.end();
          it++){
        it->first[i]+=e;
      }
      return construct(monom_rep.begin(), monom_rep.end());
    }
  };

  struct Negate
    : public CGAL::cpp98::unary_function< Polynomial_d, Polynomial_d >{

    Polynomial_d operator()(const Polynomial_d& p, int i = (d-1)) const {
      Construct_polynomial construct;
      Monomial_representation gmr;
      Monom_rep monom_rep;
      gmr(p,std::back_inserter(monom_rep));
      for(typename Monom_rep::iterator it = monom_rep.begin();
          it != monom_rep.end();
          it++){
        if (it->first[i] % 2 != 0)
          it->second = - it->second;
      }
      return construct(monom_rep.begin(), monom_rep.end());
    }
  };

  struct Invert
    : public CGAL::cpp98::unary_function< Polynomial_d , Polynomial_d >{
    Polynomial_d operator()(Polynomial_d p, int i = (PT::d-1)) const {
      if (i == (d-1)){
        p.reversal();
      }else{
        p = Swap()(p,i,PT::d-1);
        p.reversal();
        p = Swap()(p,i,PT::d-1);
      }
      return p ;
    }
  };

  struct Translate
    : public CGAL::cpp98::binary_function< Polynomial_d , Innermost_coefficient_type,
                                   Polynomial_d >{
    Polynomial_d
    operator()(
        Polynomial_d p,
        const Innermost_coefficient_type& c,
        int i = (d-1))
      const {
      if (i == (d-1) ){
        p.translate(Coefficient_type(c));
      }else{
        Swap swap;
        p = swap(p,i,d-1);
        p.translate(Coefficient_type(c));
        p = swap(p,i,d-1);
      }
      return p;
    }
  };

  struct Translate_homogeneous{
    typedef Polynomial_d result_type;
    typedef Polynomial_d first_argument_type;
    typedef Innermost_coefficient_type second_argument_type;
    typedef Innermost_coefficient_type third_argument_type;

    Polynomial_d
    operator()(Polynomial_d p,
        const Innermost_coefficient_type& a,
        const Innermost_coefficient_type& b,
        int i = (d-1) ) const {
      if (i == (d-1) ){
        p.translate(Coefficient_type(a),Coefficient_type(b));
      }else{
        Swap swap;
        p = swap(p,i,d-1);
        p.translate(Coefficient_type(a),Coefficient_type(b));
        p = swap(p,i,d-1);
      }
      return p;
    }
  };

  struct Scale
    : public CGAL::cpp98::binary_function< Polynomial_d,
                                           Innermost_coefficient_type,
                                           Polynomial_d >
  {
    Polynomial_d operator()( Polynomial_d p, const Innermost_coefficient_type& c,
        int i = (PT::d-1) ) const  {
      CGAL_precondition( i <= d-1 );
      CGAL_precondition( i >= 0 );
      typename PT::Scale_homogeneous scale_homogeneous;
      return scale_homogeneous( p, c, Innermost_coefficient_type(1), i );
    }

  };

  struct Scale_homogeneous{
    typedef Polynomial_d result_type;
    typedef Polynomial_d first_argument_type;
    typedef Innermost_coefficient_type second_argument_type;
    typedef Innermost_coefficient_type third_argument_type;

    Polynomial_d
    operator()(
        Polynomial_d p,
        const Innermost_coefficient_type& a,
        const Innermost_coefficient_type& b,
        int i = (d-1) ) const {

      CGAL_precondition( ! CGAL::is_zero(b) );
      CGAL_precondition( i <= d-1 );
      CGAL_precondition( i >= 0 );

      if (i != (d-1) ) p = Swap()(p,i,d-1);

      if(CGAL::is_one(b))
        p.scale_up(Coefficient_type(a));
      else
        if(CGAL::is_one(a))
          p.scale_down(Coefficient_type(b));
        else
          p.scale(Coefficient_type(a),Coefficient_type(b));

      if (i != (d-1) ) p = Swap()(p,i,d-1);

      return p;
    }
  };

  struct Resultant
    : public CGAL::cpp98::binary_function<Polynomial_d, Polynomial_d, Coefficient_type>{

    Coefficient_type
    operator()(
        const Polynomial_d& p,
        const Polynomial_d& q) const {
        return internal::resultant(p,q);
    }
  };

  // Polynomial subresultants (aka subresultant polynomials)
  struct Polynomial_subresultants {

    template<typename OutputIterator>
    OutputIterator operator()(
      const Polynomial_d& p,
      const Polynomial_d& q,
      OutputIterator out,
      int i = (d-1) ) const {
        if(i == (d-1) )
          return CGAL::internal::polynomial_subresultants<PT>(p,q,out);
        else
          return CGAL::internal::polynomial_subresultants<PT>(Move()(p,i),
                                                    Move()(q,i),
                                                    out);
    }
  };

  // principal subresultants (aka scalar subresultants)
  struct Principal_subresultants {

    template<typename OutputIterator>
    OutputIterator operator()(
      const Polynomial_d& p,
      const Polynomial_d& q,
      OutputIterator out,
      int i = (d-1) ) const {
        if(i == (d-1) )
          return CGAL::internal::principal_subresultants<PT>(p,q,out);
        else
          return CGAL::internal::principal_subresultants<PT>(Move()(p,i),
                                                          Move()(q,i),
                                                          out);
    }
  };

  // Subresultants with cofactors
  struct Polynomial_subresultants_with_cofactors {

    template<typename OutputIterator1,
             typename OutputIterator2,
             typename OutputIterator3>
    OutputIterator1 operator()(
      const Polynomial_d& p,
      const Polynomial_d& q,
      OutputIterator1 out_sres,
      OutputIterator2 out_co_p,
      OutputIterator3 out_co_q,
      int i = (d-1) ) const {
        if(i == (d-1) )
            return CGAL::internal::polynomial_subresultants_with_cofactors<PT>
                (p,q,out_sres,out_co_p,out_co_q);
        else
            return CGAL::internal::polynomial_subresultants_with_cofactors<PT>
                (Move()(p,i),Move()(q,i),out_sres,out_co_p,out_co_q);
    }
  };

  // Sturm-Habicht sequence (aka signed subresultant sequence)
  struct Sturm_habicht_sequence {

    template<typename OutputIterator>
    OutputIterator operator()(
      const Polynomial_d& p,
      OutputIterator out,
      int i = (d-1) ) const {
        if(i == (d-1) )
          return CGAL::internal::sturm_habicht_sequence<PT>(p,out);
        else
          return CGAL::internal::sturm_habicht_sequence<PT>(Move()(p,i),
                                                         out);
    }
  };

  //       Sturm-Habicht sequence with cofactors
  struct Sturm_habicht_sequence_with_cofactors {

    template<typename OutputIterator1,
             typename OutputIterator2,
             typename OutputIterator3>
    OutputIterator1 operator()(
      const Polynomial_d& p,
      OutputIterator1 out_stha,
      OutputIterator2 out_f,
      OutputIterator3 out_fx,
      int i = (d-1) ) const {
        if(i == (d-1) )
          return CGAL::internal::sturm_habicht_sequence_with_cofactors<PT>
              (p,out_stha,out_f,out_fx);
        else
          return CGAL::internal::sturm_habicht_sequence_with_cofactors<PT>
              (Move()(p,i),out_stha,out_f,out_fx);
    }
  };

  //       Principal Sturm-Habicht sequence (formal leading coefficients
  //       of Sturm-Habicht sequence)
  struct Principal_sturm_habicht_sequence {

    template<typename OutputIterator>
    OutputIterator operator()(
      const Polynomial_d& p,
      OutputIterator out,
      int i = (d-1) ) const {
        if(i == (d-1) )
          return CGAL::internal::principal_sturm_habicht_sequence<PT>(p,out);
        else
          return CGAL::internal::principal_sturm_habicht_sequence<PT>
              (Move()(p,i),out);
    }
  };


  // returns the Exponten_vector of the innermost leading coefficient
  struct Degree_vector{
    typedef Exponent_vector           result_type;
    typedef Polynomial_d              argument_type;

    // returns the exponent vector of inner_most_lcoeff.
    result_type operator()(const Polynomial_d& polynomial) const{
      typename PTC::Degree_vector degree_vector;
      Exponent_vector result = degree_vector(polynomial.lcoeff());
      result.push_back(polynomial.degree());
      return result;
    }
  };

    // substitute every variable by its new value in the iterator range
  // begin refers to the innermost/first variable
  struct Substitute{
  public:
    template <class Input_iterator>
    typename CGAL::Coercion_traits<
         typename std::iterator_traits<Input_iterator>::value_type,
         Innermost_coefficient_type
    >::Type
    operator()(
        const Polynomial_d& p,
        Input_iterator begin,
        Input_iterator end) const {
      typedef typename std::iterator_traits<Input_iterator> ITT;
      typedef typename ITT::iterator_category  Category;
      return (*this)(p,begin,end,Category());
    }

    template <class Input_iterator>
    typename CGAL::Coercion_traits<
         typename std::iterator_traits<Input_iterator>::value_type,
         Innermost_coefficient_type
    >::Type
    operator()(
        const Polynomial_d& p,
        Input_iterator begin,
        Input_iterator end,
        std::forward_iterator_tag) const {
      typedef typename std::iterator_traits<Input_iterator> ITT;
      std::list<typename ITT::value_type> list(begin,end);
      return (*this)(p,list.begin(),list.end());
    }

    template <class Input_iterator>
    typename
    CGAL::Coercion_traits
    <typename std::iterator_traits<Input_iterator>::value_type,
         Innermost_coefficient_type>::Type
    operator()(
        const Polynomial_d& p,
        Input_iterator begin,
        Input_iterator end,
        std::bidirectional_iterator_tag) const {

      typedef typename std::iterator_traits<Input_iterator>::value_type
        value_type;
      typedef CGAL::Coercion_traits<Innermost_coefficient_type,value_type> CT;
      typename PTC::Substitute subs;

      typename CT::Type x = typename CT::Cast()(*(--end));

      int i = Degree()(p);
      typename CT::Type y =
        subs(Get_coefficient()(p,i),begin,end);

      while (--i >= 0){
        y *= x;
        y += subs(Get_coefficient()(p,i),begin,end);
      }
      return y;
    }
  };  // substitute every variable by its new value in the iterator range



  // begin refers to the innermost/first variable
  struct Substitute_homogeneous{

    template<typename Input_iterator>
    struct Result_type{
      typedef std::iterator_traits<Input_iterator> ITT;
      typedef typename ITT::value_type value_type;
      typedef Coercion_traits<value_type, Innermost_coefficient_type> CT;
      typedef typename CT::Type Type;
    };

  public:

    template <class Input_iterator>
    typename Result_type<Input_iterator>::Type
    operator()( const Polynomial_d& p, Input_iterator begin, Input_iterator end) const{
      int hdegree = Total_degree()(p);

      typedef std::iterator_traits<Input_iterator> ITT;
      std::list<typename ITT::value_type> list(begin,end);

      // make the homogeneous variable the first in the list
      list.push_front(list.back());
      list.pop_back();

      // reverse and begin with the outermost variable
      return (*this)(p, list.rbegin(), list.rend(), hdegree);
    }

    // this operator is undcoumented and for internal use:
    // the iterator range starts with the outermost variable
    // and ends with the homogeneous variable
    template <class Input_iterator>
    typename Result_type<Input_iterator>::Type
    operator()(
        const Polynomial_d& p,
        Input_iterator begin,
        Input_iterator end,
        int hdegree) const{


      typedef std::iterator_traits<Input_iterator> ITT;
      typedef typename ITT::value_type value_type;
      typedef Coercion_traits<value_type, Innermost_coefficient_type> CT;

      typename PTC::Substitute_homogeneous subsh;

      typename CT::Type x = typename CT::Cast()(*begin++);


      int i = Degree()(p);
      typename CT::Type y = subsh(Get_coefficient()(p,i),begin,end, hdegree-i);

      while (--i >= 0){
        y *= x;
        y += subsh(Get_coefficient()(p,i),begin,end,hdegree-i);
      }
      return y;
    }
  };

};

} // namespace internal

// Definition of Polynomial_traits_d
//
// In order to determine the algebraic category of the innermost coefficient,
// the Polynomial_traits_d_base class with "Null_tag" is used.

template< class Polynomial >
class Polynomial_traits_d
  : public internal::Polynomial_traits_d_base< Polynomial,
    typename Algebraic_structure_traits<
typename internal::Innermost_coefficient_type<Polynomial>::Type >::Algebraic_category,
    typename Algebraic_structure_traits< Polynomial >::Algebraic_category > ,
  public Algebraic_structure_traits<Polynomial>{

//------------ Rebind -----------
private:
  template <class T, int d>
  struct Gen_polynomial_type{
    typedef CGAL::Polynomial<typename Gen_polynomial_type<T,d-1>::Type> Type;
  };
  template <class T>
  struct Gen_polynomial_type<T,0>{ typedef T Type; };

public:
  template <class T, int d>
  struct Rebind{
    typedef Polynomial_traits_d<typename Gen_polynomial_type<T,d>::Type> Other;
  };
//------------ Rebind -----------
};

} //namespace CGAL

#include <CGAL/enable_warnings.h>

#endif // CGAL_POLYNOMIAL_TRAITS_D_H

