// Copyright (c) 2001-2006  INRIA Sophia-Antipolis (France).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org)
//
// $URL: https://github.com/CGAL/cgal/blob/v6.1.2/Number_types/include/CGAL/NT_converter.h $
// $Id: include/CGAL/NT_converter.h 37e2b278910 $
// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s)     : Sylvain Pion

#ifndef CGAL_NT_CONVERTER_H
#define CGAL_NT_CONVERTER_H

#include <CGAL/number_type_config.h>
#include <CGAL/number_utils.h>

#include <functional>

namespace CGAL {

template <bool>
class Interval_nt;

template <class NT>
class Quotient;

// A number type converter usable as default, using the conversion operator.
template < class NT1, class NT2 >
struct NT_converter
  : public CGAL::cpp98::unary_function< NT1, NT2 >
{
    NT2
    operator()(const NT1 &a) const
    {
        return NT2(a);
    }
};

// Some specializations for :
// - double to call to_double().
// - Interval_nt<> to call to_interval().
// - NT1 == NT2 to return a reference instead of copying.
// - Quotient conversions

template < class NT1 >
struct NT_converter < NT1, NT1 >
  : public CGAL::cpp98::unary_function< NT1, NT1 >
{
    const NT1 &
    operator()(const NT1 &a) const
    {
        return a;
    }
};

template < class NT1 >
struct NT_converter < NT1, double >
  : public CGAL::cpp98::unary_function< NT1, double >
{
    double
    operator()(const NT1 &a) const
    {
        return CGAL_NTS to_double(a);
    }
};

template < class NT1 >
struct NT_converter < NT1, float >
  : public CGAL::cpp98::unary_function< NT1, float >
{
    float
    operator()(const NT1 &a) const
    {
        return static_cast<float>(to_double(a));
    }
};

template <>
struct NT_converter < double, double >
  : public CGAL::cpp98::unary_function< double, double >
{
    const double &
    operator()(const double &a) const
    {
        return a;
    }
};

template <>
struct NT_converter < float, float >
  : public CGAL::cpp98::unary_function< float, float >
{
    const float &
    operator()(const float &a) const
    {
        return a;
    }
};

template < class NT1, bool b >
struct NT_converter < NT1, Interval_nt<b> >
  : public CGAL::cpp98::unary_function< NT1, Interval_nt<b> >
{
    Interval_nt<b>
    operator()(const NT1 &a) const
    {
        return CGAL_NTS to_interval(a);
    }
};

template < bool b >
struct NT_converter < Interval_nt<b>, Interval_nt<b> >
  : public CGAL::cpp98::unary_function< Interval_nt<b>, Interval_nt<b> >
{
    const Interval_nt<b> &
    operator()(const Interval_nt<b> &a) const
    {
        return a;
    }
};

template < class NT >
struct NT_converter < Quotient<NT>, Quotient<NT> >
  : public CGAL::cpp98::unary_function< Quotient<NT>, Quotient<NT> >
{
    const Quotient<NT>&
    operator()(const Quotient<NT> & q) const
    {
        return q;
    }
};

template < class NT1, class NT2 >
struct NT_converter < Quotient<NT1>, Quotient<NT2> >
  : public CGAL::cpp98::unary_function< Quotient<NT1>, Quotient<NT2> >
{
    Quotient<NT2>
    operator()(const Quotient<NT1> & q) const
    {
        NT_converter < NT1, NT2 > nt;
        return Quotient<NT2>(nt(q.numerator()), nt(q.denominator()));
    }
};

} //namespace CGAL

#endif // CGAL_NT_CONVERTER_H
