// Copyright (c) 1998-2005,2007  
// Utrecht University (The Netherlands),
// ETH Zurich (Switzerland),
// INRIA Sophia-Antipolis (France),
// Max-Planck-Institute Saarbruecken (Germany),
// and Tel-Aviv University (Israel).  All rights reserved. 
//
// This file is part of CGAL (www.cgal.org); you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public License as
// published by the Free Software Foundation; either version 3 of the License,
// or (at your option) any later version.
//
// Licensees holding a valid commercial license may use this file in
// accordance with the commercial license agreement provided with the software.
//
// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
//
// $URL$
// $Id$
// SPDX-License-Identifier: LGPL-3.0+
//
//
// Author(s)     : Sylvain Pion, Michael Hemmer

#ifndef CGAL_INTERVAL_NT_H
#define CGAL_INTERVAL_NT_H

// This file contains the description of the following classes:
// - Interval_nt<false>  It's a number type that needs the FPU rounding mode
//                       to be set to +inf.  It is also typedef'd to
//                       Interval_nt_advanced for backward compatibility.
// - Interval_nt<true>   Same but it does the rounding mode itself so you
//                       don't have to worry about it.  But it's slower.
//
// Note: When rounding is towards +infinity, to make an operation rounded
// towards -infinity, it's enough to take the opposite of some of the operand,
// and the opposite of the result (see operator+, operator*,...).

// TODO : 
// - test whether stopping constant propagation only in functions taking
//   double as arguments, improves performance.

#include <utility> // for std::pair
#include <CGAL/number_type_config.h>
#include <CGAL/number_utils.h>
#include <CGAL/utils_classes.h>
#include <CGAL/number_utils.h>
#include <CGAL/Uncertain.h>
#include <CGAL/Interval_traits.h>
#include <CGAL/double.h>
#include <CGAL/FPU.h>
#include <CGAL/IO/io.h>
#include <iostream>

namespace CGAL {

template <bool Protected = true>
class Interval_nt
{
  typedef Interval_nt<Protected>     IA;
  typedef std::pair<double, double>  Pair;

public:

  typedef double      value_type;

  typedef Uncertain_conversion_exception            unsafe_comparison;
  typedef Checked_protect_FPU_rounding<Protected>   Internal_protector;
  typedef Protect_FPU_rounding<!Protected>          Protector;

  Interval_nt()
#ifndef CGAL_NO_ASSERTIONS
      : _inf(1), _sup(0)
             // to early and deterministically detect use of uninitialized
#endif
    {}

  Interval_nt(int i)
    : _inf(i), _sup(i) {}

  Interval_nt(unsigned i)
    : _inf(i), _sup(i) {}

  Interval_nt(long long i)
    : _inf(static_cast<double>(i)), _sup(static_cast<double>(i))
  {
    // gcc ignores -frounding-math when converting integers to floats.
#ifdef __GNUC__
    long long safe = 1LL << 52; // Use numeric_limits?
    bool exact = ((long long)_inf == i) || (i <= safe && i >= -safe);
    if (!(__builtin_constant_p(exact) && exact))
#endif
      *this += smallest();
  }

  Interval_nt(unsigned long long i)
    : _inf(static_cast<double>(i)), _sup(static_cast<double>(i))
  {
#ifdef __GNUC__
    unsigned long long safe = 1ULL << 52; // Use numeric_limits?
    bool exact = ((unsigned long long)_inf == i) || (i <= safe);
    if (!(__builtin_constant_p(exact) && exact))
#endif
      *this += smallest();
  }

  Interval_nt(long i)
  {
    *this = (sizeof(int)==sizeof(long)) ?
      Interval_nt((int)i) :
      Interval_nt((long long)i);
  }

  Interval_nt(unsigned long i)
  {
    *this = (sizeof(int)==sizeof(long)) ?
      Interval_nt((unsigned)i) :
      Interval_nt((unsigned long long)i);
  }

  Interval_nt(double d)
    : _inf(d), _sup(d) { CGAL_assertion(is_finite(d)); }

// The Intel compiler on Linux is aggressive with constant propagation and
// it seems there is no flag to stop it, so disable this check for it.
#if !defined(CGAL_DISABLE_ROUNDING_MATH_CHECK) && \
    defined(__INTEL_COMPILER) && defined(__linux)
#  define CGAL_DISABLE_ROUNDING_MATH_CHECK
#endif

  Interval_nt(double i, double s)
    : _inf(i), _sup(s)
  {
    // Previously it was:
    //    CGAL_assertion_msg(!(i>s);
    // But MSVC++ 2012 optimizes the test "!(i>s)" to "i<=s", even with
    // /fp:strict. If 'i' or 's' is a NaN, that makes a difference.
    CGAL_assertion_msg( (!is_valid(i)) || (!is_valid(s)) || (!(i>s)),
	      " Variable used before being initialized (or CGAL bug)");
#ifndef CGAL_DISABLE_ROUNDING_MATH_CHECK
    CGAL_assertion_code((void) tester;) // Necessary to trigger a runtime test of rounding modes.
#endif
  }

  Interval_nt(const Pair & p)
    : _inf(p.first), _sup(p.second) {}

  IA operator-() const { return IA (-sup(), -inf()); }

  IA & operator+= (const IA &d) { return *this = *this + d; }
  IA & operator-= (const IA &d) { return *this = *this - d; }
  IA & operator*= (const IA &d) { return *this = *this * d; }
  IA & operator/= (const IA &d) { return *this = *this / d; }

  bool is_point() const
  {
    return sup() == inf();
  }

  bool is_same (const IA & d) const
  {
    return inf() == d.inf() && sup() == d.sup();
  }

  bool do_overlap (const IA & d) const
  {
    return !(d.inf() > sup() || d.sup() < inf());
  }

  const double & inf() const { return _inf; }
  const double & sup() const { return _sup; }

  std::pair<double, double> pair() const
  {
    return std::pair<double, double>(inf(), sup());
  }

  static IA largest()
  {
    return IA(-std::numeric_limits<double>::infinity(), std::numeric_limits<double>::infinity());
  }

  static IA smallest()
  {
    return IA(-CGAL_IA_MIN_DOUBLE, CGAL_IA_MIN_DOUBLE);
  }

#if 0 // def CGAL_HISTOGRAM_PROFILER  // not yet ready
  ~Interval_nt()
  {
    CGAL_HISTOGRAM_PROFILER("[Interval_nt relative precision in log2 scale]",
                             (unsigned) ( ::log(relative_precision(*this))) / ::log(2.0) )  );
  }
#endif

private:
  // Pair inf_sup;
  double _inf, _sup;

  struct Test_runtime_rounding_modes {
    Test_runtime_rounding_modes()
    {
      // We test whether GCC's -frounding-math option has been forgotten.
      // The macros CGAL_IA_MUL and CGAL_IA_DIV stop constant propagation only
      // on the second argument, so if -fno-rounding-math, the compiler optimizes
      // the 2 negations and we get wrong rounding.
      typename Interval_nt<>::Internal_protector P;
      CGAL_assertion_msg(-CGAL_IA_MUL(-1.1, 10.1) != CGAL_IA_MUL(1.1, 10.1),
                         "Wrong rounding: did you forget the  -frounding-math  option if you use GCC (or  -fp-model strict  for Intel)?");
      CGAL_assertion_msg(-CGAL_IA_DIV(-1., 10) != CGAL_IA_DIV(1., 10),
                         "Wrong rounding: did you forget the  -frounding-math  option if you use GCC (or  -fp-model strict  for Intel)?");
    }
  };

#ifndef CGAL_DISABLE_ROUNDING_MATH_CHECK
  static const Test_runtime_rounding_modes tester;
#endif
};

#ifndef CGAL_DISABLE_ROUNDING_MATH_CHECK
template <bool Protected>
const typename Interval_nt<Protected>::Test_runtime_rounding_modes
Interval_nt<Protected>::tester;
#endif

template <bool Protected>
inline
Uncertain<bool>
operator<(const Interval_nt<Protected> &a, const Interval_nt<Protected> &b)
{
  if (a.sup()  < b.inf()) return true;
  if (a.inf() >= b.sup()) return false;
  return Uncertain<bool>::indeterminate();
}

template <bool Protected>
inline
Uncertain<bool>
operator>(const Interval_nt<Protected> &a, const Interval_nt<Protected> &b)
{ return b < a; }

template <bool Protected>
inline
Uncertain<bool>
operator<=(const Interval_nt<Protected> &a, const Interval_nt<Protected> &b)
{
  if (a.sup() <= b.inf()) return true;
  if (a.inf() >  b.sup()) return false;
  return Uncertain<bool>::indeterminate();
}

template <bool Protected>
inline
Uncertain<bool>
operator>=(const Interval_nt<Protected> &a, const Interval_nt<Protected> &b)
{ return b <= a; }

template <bool Protected>
inline
Uncertain<bool>
operator==(const Interval_nt<Protected> &a, const Interval_nt<Protected> &b)
{
  if (b.inf() >  a.sup() || b.sup() <  a.inf()) return false;
  if (b.inf() == a.sup() && b.sup() == a.inf()) return true;
  return Uncertain<bool>::indeterminate();
}

template <bool Protected>
inline
Uncertain<bool>
operator!=(const Interval_nt<Protected> &a, const Interval_nt<Protected> &b)
{ return ! (a == b); }


// Mixed operators with double.

template <bool Protected>
inline
Uncertain<bool>
operator<(double a, const Interval_nt<Protected> &b)
{
  if (a < b.inf()) return true;
  if (a >= b.sup()) return false;
  return Uncertain<bool>::indeterminate();
}

template <bool Protected>
inline
Uncertain<bool>
operator>(double a, const Interval_nt<Protected> &b)
{ return b < a; }

template <bool Protected>
inline
Uncertain<bool>
operator<=(double a, const Interval_nt<Protected> &b)
{
  if (a <= b.inf()) return true;
  if (a >  b.sup()) return false;
  return Uncertain<bool>::indeterminate();
}

template <bool Protected>
inline
Uncertain<bool>
operator>=(double a, const Interval_nt<Protected> &b)
{ return b <= a; }

template <bool Protected>
inline
Uncertain<bool>
operator==(double a, const Interval_nt<Protected> &b)
{
  if (b.inf() >  a || b.sup() <  a) return false;
  if (b.inf() == a && b.sup() == a) return true;
  return Uncertain<bool>::indeterminate();
}

template <bool Protected>
inline
Uncertain<bool>
operator!=(double a, const Interval_nt<Protected> &b)
{ return ! (a == b); }

template <bool Protected>
inline
Uncertain<bool>
operator<(const Interval_nt<Protected> &a, double b)
{
  if (a.sup()  < b) return true;
  if (a.inf() >= b) return false;
  return Uncertain<bool>::indeterminate();
}

template <bool Protected>
inline
Uncertain<bool>
operator>(const Interval_nt<Protected> &a, double b)
{ return b < a; }

template <bool Protected>
inline
Uncertain<bool>
operator<=(const Interval_nt<Protected> &a, double b)
{
  if (a.sup() <= b) return true;
  if (a.inf() >  b) return false;
  return Uncertain<bool>::indeterminate();
}

template <bool Protected>
inline
Uncertain<bool>
operator>=(const Interval_nt<Protected> &a, double b)
{ return b <= a; }

template <bool Protected>
inline
Uncertain<bool>
operator==(const Interval_nt<Protected> &a, double b)
{
  if (b >  a.sup() || b <  a.inf()) return false;
  if (b == a.sup() && b == a.inf()) return true;
  return Uncertain<bool>::indeterminate();
}

template <bool Protected>
inline
Uncertain<bool>
operator!=(const Interval_nt<Protected> &a, double b)
{ return ! (a == b); }



// Non-documented
// Returns true if the interval is a unique representable double.
template <bool Protected>
inline
bool
fit_in_double (const Interval_nt<Protected> & d, double &r)
{
  bool b = d.is_point();
  if (b)
    r = d.inf();
  return b;
}

// Non-documented
template <bool Protected>
inline
bool
is_singleton (const Interval_nt<Protected> & d)
{
  return d.is_point();
}

// Non-documented
template <bool Protected>
inline
double
magnitude (const Interval_nt<Protected> & d)
{
  return (std::max)(CGAL::abs(d.inf()), CGAL::abs(d.sup()));
}

// Non-documented
template <bool Protected>
inline
double
width (const Interval_nt<Protected> & d)
{
  return d.sup() - d.inf();
}

// Non-documented
template <bool Protected>
inline
double
radius (const Interval_nt<Protected> & d)
{
  return width(d)/2; // This could be improved to avoid overflow.
}

// Non-documented
// This is the relative precision of to_double() (the center of the interval),
// hence we use radius() instead of width().
template <bool Protected>
inline
bool
has_smaller_relative_precision(const Interval_nt<Protected> & d, double prec)
{
  return magnitude(d) == 0 || radius(d) < prec * magnitude(d);
}

// Non-documented
template <bool Protected>
double
relative_precision(const Interval_nt<Protected> & d)
{
  if (magnitude(d) == 0.0)
    return 0.0;
  return radius(d) / magnitude(d);
}


template< bool Protected >
class Is_valid< Interval_nt<Protected> >
  : public CGAL::cpp98::unary_function< Interval_nt<Protected>, bool > {
  public :
    bool operator()( const Interval_nt<Protected>& x ) const {
      return is_valid(x.inf()) &&
             is_valid(x.sup()) &&
             x.inf() <= x.sup();
    }
};

template <bool Protected>
std::ostream & operator<< (std::ostream &os, const Interval_nt<Protected> & I )
{
  return os << "[" << I.inf() << ";" << I.sup() << "]";
}

#define CGAL_SWALLOW(IS,CHAR)                           \
    {                                                   \
        char c;                                         \
        do is.get(c); while (isspace(c));            \
        if (c != CHAR) {                                \
            is.setstate(std::ios_base::failbit);        \
        }                                               \
    }                                                   \

template <bool Protected>
std::istream & operator>> (std::istream &is, Interval_nt<Protected> & I)
{
    char c;
    do is.get(c); while (isspace(c));
    is.putback(c);
    if(c == '['){ // read original output from operator <<
        double inf,sup;
        CGAL_SWALLOW(is, '[');// read the "["
        is >> iformat(inf);
        CGAL_SWALLOW(is, ';');// read the ";"
        is >> iformat(sup);
        CGAL_SWALLOW(is, ']');// read the "]"
        I = Interval_nt<Protected>(inf,sup);
    }else{ //read double (backward compatibility)
        double d;
        is >> d;
        I = d;
    }
    return is;
}
#undef CGAL_SWALLOW

typedef Interval_nt<false> Interval_nt_advanced;  // for backward-compatibility


template <bool Protected>
inline
Interval_nt<Protected>
operator+ (const Interval_nt<Protected> &a, const Interval_nt<Protected> & b)
{
  typename Interval_nt<Protected>::Internal_protector P;
  return Interval_nt<Protected> (-CGAL_IA_SUB(-a.inf(), b.inf()),
                                  CGAL_IA_ADD(a.sup(), b.sup()));
}

template <bool Protected>
inline
Interval_nt<Protected>
operator+ (double a, const Interval_nt<Protected> & b)
{
  return Interval_nt<Protected>(a)+b;
}

template <bool Protected>
inline
Interval_nt<Protected>
operator+ (const Interval_nt<Protected> & a, double b)
{
  return a+Interval_nt<Protected>(b);
}

template< bool Protected >
inline
Interval_nt<Protected>
operator+( const Interval_nt<Protected>& a ) {
  return a;
}

template <bool Protected>
inline
Interval_nt<Protected>
operator- (const Interval_nt<Protected> &a, const Interval_nt<Protected> & b)
{
  typename Interval_nt<Protected>::Internal_protector P;
  return Interval_nt<Protected>(-CGAL_IA_SUB(b.sup(), a.inf()),
                                 CGAL_IA_SUB(a.sup(), b.inf()));
}

template <bool Protected>
inline
Interval_nt<Protected>
operator- (double a, const Interval_nt<Protected> & b)
{
  return Interval_nt<Protected>(a)-b;
}

template <bool Protected>
inline
Interval_nt<Protected>
operator- (const Interval_nt<Protected> & a, double b)
{
  return a-Interval_nt<Protected>(b);
}

template <bool Protected>
inline
Interval_nt<Protected>
operator* (const Interval_nt<Protected> &a, const Interval_nt<Protected> & b)
{
  typedef Interval_nt<Protected> IA;
  typename Interval_nt<Protected>::Internal_protector P;
  if (a.inf() >= 0.0)					// a>=0
  {
    // b>=0     [a.inf()*b.inf(); a.sup()*b.sup()]
    // b<=0     [a.sup()*b.inf(); a.inf()*b.sup()]
    // b~=0     [a.sup()*b.inf(); a.sup()*b.sup()]
    double aa = a.inf(), bb = a.sup();
    if (b.inf() < 0.0)
    {
	aa = bb;
	if (b.sup() < 0.0)
	    bb = a.inf();
    }
    return IA(-CGAL_IA_MUL(aa, -b.inf()), CGAL_IA_MUL(bb, b.sup()));
  }
  else if (a.sup()<=0.0)				// a<=0
  {
    // b>=0     [a.inf()*b.sup(); a.sup()*b.inf()]
    // b<=0     [a.sup()*b.sup(); a.inf()*b.inf()]
    // b~=0     [a.inf()*b.sup(); a.inf()*b.inf()]
    double aa = a.sup(), bb = a.inf();
    if (b.inf() < 0.0)
    {
	aa=bb;
	if (b.sup() < 0.0)
	    bb=a.sup();
    }
    return IA(-CGAL_IA_MUL(bb, -b.sup()), CGAL_IA_MUL(aa, b.inf()));
  }
  else						// 0 \in a
  {
    if (b.inf()>=0.0)				// b>=0
      return IA(-CGAL_IA_MUL(a.inf(), -b.sup()),
                 CGAL_IA_MUL(a.sup(), b.sup()));
    if (b.sup()<=0.0)				// b<=0
      return IA(-CGAL_IA_MUL(a.sup(), -b.inf()),
                 CGAL_IA_MUL(a.inf(), b.inf()));
        					// 0 \in b
    double tmp1 = CGAL_IA_MUL(a.inf(), -b.sup());
    double tmp2 = CGAL_IA_MUL(a.sup(), -b.inf());
    double tmp3 = CGAL_IA_MUL(a.inf(),  b.inf());
    double tmp4 = CGAL_IA_MUL(a.sup(),  b.sup());
    return IA(-(std::max)(tmp1,tmp2), (std::max)(tmp3,tmp4));
  }
}

template <bool Protected>
inline
Interval_nt<Protected>
operator* (double a, const Interval_nt<Protected> & b)
{
  return Interval_nt<Protected>(a)*b;
}

template <bool Protected>
inline
Interval_nt<Protected>
operator* (const Interval_nt<Protected> & a, double b)
{
  return a*Interval_nt<Protected>(b);
}

template <bool Protected>
inline
Interval_nt<Protected>
operator/ (const Interval_nt<Protected> &a, const Interval_nt<Protected> & b)
{
  typedef Interval_nt<Protected> IA;
  typename Interval_nt<Protected>::Internal_protector P;
  if (b.inf() > 0.0)				// b>0
  {
    // e>=0	[a.inf()/b.sup(); a.sup()/b.inf()]
    // e<=0	[a.inf()/b.inf(); a.sup()/b.sup()]
    // e~=0	[a.inf()/b.inf(); a.sup()/b.inf()]
    double aa = b.sup(), bb = b.inf();
    if (a.inf() < 0.0)
    {
	aa = bb;
	if (a.sup() < 0.0)
	    bb = b.sup();
    }
    return IA(-CGAL_IA_DIV(a.inf(), -aa), CGAL_IA_DIV(a.sup(), bb));
  }
  else if (b.sup()<0.0)			// b<0
  {
    // e>=0	[a.sup()/b.sup(); a.inf()/b.inf()]
    // e<=0	[a.sup()/b.inf(); a.inf()/b.sup()]
    // e~=0	[a.sup()/b.sup(); a.inf()/b.sup()]
    double aa = b.sup(), bb = b.inf();
    if (a.inf() < 0.0)
    {
	bb = aa;
	if (a.sup() < 0.0)
	    aa = b.inf();
    }
    return IA(-CGAL_IA_DIV(a.sup(), -aa), CGAL_IA_DIV(a.inf(), bb));
  }
  else					// b~0
    return IA::largest();
	   // We could do slightly better -> [0;infinity] when b.sup()==0,
	   // but is this worth ?
}

template <bool Protected>
inline
Interval_nt<Protected>
operator/ (double a, const Interval_nt<Protected> & b)
{
  return Interval_nt<Protected>(a)/b;
}

template <bool Protected>
inline
Interval_nt<Protected>
operator/ (const Interval_nt<Protected> & a, double b)
{
  return a/Interval_nt<Protected>(b);
}

// TODO: What about these two guys? Where do they belong to?
template <bool Protected>
struct Min <Interval_nt<Protected> >
    : public CGAL::cpp98::binary_function<Interval_nt<Protected>,
                             Interval_nt<Protected>,
                             Interval_nt<Protected> >
{
    Interval_nt<Protected> operator()( const Interval_nt<Protected>& d,
                                       const Interval_nt<Protected>& e) const
    {
        return Interval_nt<Protected>(
                (std::min)(d.inf(), e.inf()),
                (std::min)(d.sup(), e.sup()));
    }
};

template <bool Protected>
struct Max <Interval_nt<Protected> >
    : public CGAL::cpp98::binary_function<Interval_nt<Protected>,
                             Interval_nt<Protected>,
                             Interval_nt<Protected> >
{
    Interval_nt<Protected> operator()( const Interval_nt<Protected>& d,
                                       const Interval_nt<Protected>& e) const
    {
        return Interval_nt<Protected>(
                (std::max)(d.inf(), e.inf()),
                (std::max)(d.sup(), e.sup()));
    }
};

template<bool Protected> inline 
Interval_nt<Protected> min BOOST_PREVENT_MACRO_SUBSTITUTION(
const Interval_nt<Protected> & x,
const Interval_nt<Protected> & y){
  return CGAL::Min<Interval_nt<Protected> > ()(x,y);
}
template<bool Protected> inline 
Interval_nt<Protected> max BOOST_PREVENT_MACRO_SUBSTITUTION(
const Interval_nt<Protected> & x,
const Interval_nt<Protected> & y){
  return CGAL::Max<Interval_nt<Protected> > ()(x,y);
}



// TODO : document, when we are OK with the interface.
// - should it allow other number types for the exponent ?
template < bool b >
Interval_nt<b>
ldexp(const Interval_nt<b> &i, int e)
{
  double scale = std::ldexp(1.0, e);
  Interval_nt<b> scale_interval (
                      CGAL_NTS is_finite(scale) ? scale : CGAL_IA_MAX_DOUBLE,
                      scale == 0 ? CGAL_IA_MIN_DOUBLE : scale);
  return i * scale_interval;
}


// We also specialize some corresponding functors returning Uncertain<>.

// TODO: To which concept do these functors belong? Can we remove them??
template < bool b >
struct Equal_to < Interval_nt<b>, Interval_nt<b> >
  : public CGAL::cpp98::binary_function< Interval_nt<b>, Interval_nt<b>, Uncertain<bool> >
{
  Uncertain<bool> operator()( const Interval_nt<b>& x,
                              const Interval_nt<b>& y) const
  { return x == y; }
};

template < bool b >
struct Not_equal_to < Interval_nt<b>, Interval_nt<b> >
  : public CGAL::cpp98::binary_function< Interval_nt<b>, Interval_nt<b>, Uncertain<bool> >
{
  Uncertain<bool> operator()( const Interval_nt<b>& x,
                              const Interval_nt<b>& y) const
  { return x != y; }
};

template < bool b >
struct Greater < Interval_nt<b>, Interval_nt<b> >
  : public CGAL::cpp98::binary_function< Interval_nt<b>, Interval_nt<b>, Uncertain<bool> >
{
  Uncertain<bool> operator()( const Interval_nt<b>& x,
                              const Interval_nt<b>& y) const
  { return x > y; }
};

template < bool b >
struct Less < Interval_nt<b>, Interval_nt<b> >
  : public CGAL::cpp98::binary_function< Interval_nt<b>, Interval_nt<b>, Uncertain<bool> >
{
  Uncertain<bool> operator()( const Interval_nt<b>& x,
                              const Interval_nt<b>& y) const
  { return x < y; }
};

template < bool b >
struct Greater_equal < Interval_nt<b>, Interval_nt<b> >
  : public CGAL::cpp98::binary_function< Interval_nt<b>, Interval_nt<b>, Uncertain<bool> >
{
  Uncertain<bool> operator()( const Interval_nt<b>& x,
                              const Interval_nt<b>& y) const
  { return x >= y; }
};

template < bool b >
struct Less_equal < Interval_nt<b>, Interval_nt<b> >
  : public CGAL::cpp98::binary_function< Interval_nt<b>, Interval_nt<b>, Uncertain<bool> >
{
  Uncertain<bool> operator()( const Interval_nt<b>& x,
                              const Interval_nt<b>& y) const
  { return x <= y; }
};


// As in MP_float.h, the namespace INTERN_INTERVAL_NT contains (now) global
// functions like square or sqrt which would have collided with the new
// global functions from AST/RET
//
// TODO: IMHO, a better solution would be to put the INTERN_MP_FLOAT-functions
//       into the MP_Float-class... But there is surely a reason why this is not
//       the case..?


namespace INTERN_INTERVAL_NT {

  template <bool Protected>
  inline
  double
  to_double (const Interval_nt<Protected> & d)
  {
    return (d.sup() + d.inf()) * 0.5;
    // This may overflow...
  }

  template <bool Protected>
  inline
  std::pair<double, double>
  to_interval (const Interval_nt<Protected> & d)
  {
    return d.pair();
  }

  template <bool Protected>
  inline
  Interval_nt<Protected>
  sqrt (const Interval_nt<Protected> & d)
  {
    typename Interval_nt<Protected>::Internal_protector P;  // not optimal here.
    // sqrt([+a,+b]) => [sqrt(+a);sqrt(+b)]
    // sqrt([-a,+b]) => [0;sqrt(+b)] => assumes roundoff error.
    // sqrt([-a,-b]) => [0;sqrt(-b)] => assumes user bug (unspecified result).
    FPU_set_cw(CGAL_FE_DOWNWARD);
    double i = (d.inf() > 0.0) ? CGAL_IA_SQRT(d.inf()) : 0.0;
    FPU_set_cw(CGAL_FE_UPWARD);
    return Interval_nt<Protected>(i, CGAL_IA_SQRT(d.sup()));
  }

  template <bool Protected>
  inline
  Interval_nt<Protected>
  square (const Interval_nt<Protected> & d)
  {
    typename Interval_nt<Protected>::Internal_protector P;
    if (d.inf()>=0.0)
        return Interval_nt<Protected>(-CGAL_IA_MUL(d.inf(), -d.inf()),
                                 CGAL_IA_MUL(d.sup(), d.sup()));
    if (d.sup()<=0.0)
        return Interval_nt<Protected>(-CGAL_IA_MUL(d.sup(), -d.sup()),
                               CGAL_IA_MUL(d.inf(), d.inf()));
    return Interval_nt<Protected>(0.0, CGAL_IA_SQUARE((std::max)(-d.inf(),
                     d.sup())));
  }

  template <bool Protected>
  inline
  Interval_nt<Protected>
  abs (const Interval_nt<Protected> & d)
  {
    if (d.inf() >= 0.0) return d;
    if (d.sup() <= 0.0) return -d;
    return Interval_nt<Protected>(0.0, (std::max)(-d.inf(), d.sup()));
  }

  template <bool Protected>
  inline
  Uncertain<Sign>
  sign (const Interval_nt<Protected> & d)
  {
    if (d.inf() > 0.0) return POSITIVE;
    if (d.sup() < 0.0) return NEGATIVE;
    if (d.inf() == d.sup()) return ZERO;
    return Uncertain<Sign>::indeterminate();
  }

  template <bool Protected>
  inline
  Uncertain<Comparison_result>
  compare (const Interval_nt<Protected> & d, const Interval_nt<Protected> & e)
  {
    if (d.inf() > e.sup()) return LARGER;
    if (e.inf() > d.sup()) return SMALLER;
    if (e.inf() == d.sup() && d.inf() == e.sup()) return EQUAL;
    return Uncertain<Comparison_result>::indeterminate();
  }

  template <bool Protected>
  inline
  Uncertain<bool>
  is_zero (const Interval_nt<Protected> & d)
  {
    if (d.inf() > 0.0) return false;
    if (d.sup() < 0.0) return false;
    if (d.inf() == d.sup()) return true;
    return Uncertain<bool>::indeterminate();
  }

  template <bool Protected>
  inline
  Uncertain<bool>
  is_one (const Interval_nt<Protected> & d)
  {
    if (d.inf() > 1) return false;
    if (d.sup() < 1) return false;
    if (d.inf() == d.sup()) return true;
    return Uncertain<bool>::indeterminate();
  }

  template <bool Protected>
  inline
  Uncertain<bool>
  is_positive (const Interval_nt<Protected> & d)
  {
    if (d.inf() > 0.0) return true;
    if (d.sup() <= 0.0) return false;
    return Uncertain<bool>::indeterminate();
  }

  template <bool Protected>
  inline
  Uncertain<bool>
  is_negative (const Interval_nt<Protected> & d)
  {
    if (d.inf() >= 0.0) return false;
    if (d.sup() < 0.0) return true;
    return Uncertain<bool>::indeterminate();
  }

} // namespace INTERN_INTERVAL_NT


template< bool B > class Real_embeddable_traits< Interval_nt<B> >
  : public INTERN_RET::Real_embeddable_traits_base< Interval_nt<B> , CGAL::Tag_true> {
  public:
    typedef Interval_nt<B>  Type;
  typedef Uncertain<CGAL::Sign> Sign;
  typedef Uncertain<bool> Boolean;
  typedef Uncertain<CGAL::Comparison_result> Comparison_result; 

    class Abs
      : public CGAL::cpp98::unary_function< Type, Type > {
      public:
        Type operator()( const Type& x ) const {
            return INTERN_INTERVAL_NT::abs( x );
        }
    };

    class Sgn
        : public CGAL::cpp98::unary_function< Type, Uncertain< ::CGAL::Sign > > {
      public:
        Uncertain< ::CGAL::Sign > operator()( const Type& x ) const {
            return INTERN_INTERVAL_NT::sign( x );
        }
    };

    class Is_positive
      : public CGAL::cpp98::unary_function< Type, Uncertain<bool> > {
      public:
        Uncertain<bool> operator()( const Type& x ) const {
          return INTERN_INTERVAL_NT::is_positive( x );
        }
    };

    class Is_negative
      : public CGAL::cpp98::unary_function< Type, Uncertain<bool> > {
      public:
        Uncertain<bool> operator()( const Type& x ) const {
          return INTERN_INTERVAL_NT::is_negative( x );
        }
    };

    class Compare
      : public CGAL::cpp98::binary_function< Type, Type, Comparison_result > {
      public:
      Comparison_result operator()( const Type& x, const Type& y ) const {
        return INTERN_INTERVAL_NT::compare( x, y );
      }
      CGAL_IMPLICIT_INTEROPERABLE_BINARY_OPERATOR_WITH_RT( Type,
          Comparison_result )
    };

    class To_double
      : public CGAL::cpp98::unary_function< Type, double > {
      public:
        double operator()( const Type& x ) const {
            return INTERN_INTERVAL_NT::to_double( x );
        }
    };

    class To_interval
      : public CGAL::cpp98::unary_function< Type, std::pair< double, double > > {
      public:
        std::pair<double, double> operator()( const Type& x ) const {
            return INTERN_INTERVAL_NT::to_interval( x );
        }
    };

    class Is_finite
      : public CGAL::cpp98::unary_function< Type, Boolean > {
      public :
        Boolean operator()( const Type& x ) const {
          return CGAL_NTS is_finite( x.inf() ) && CGAL_NTS is_finite( x.sup() );
        }
    };

};

// Algebraic structure traits
template< bool B >
class Algebraic_structure_traits< Interval_nt<B> >
  : public Algebraic_structure_traits_base< Interval_nt<B>,
                                            Field_with_sqrt_tag >  {
  public:
    typedef Interval_nt<B>      Type;
    typedef Tag_false           Is_exact;
    typedef Tag_true            Is_numerical_sensitive;
    typedef Uncertain<bool>     Boolean; 

    class Is_zero
      : public CGAL::cpp98::unary_function< Type, Boolean > {
      public:
        Boolean operator()( const Type& x ) const {
          return INTERN_INTERVAL_NT::is_zero( x );
        }
    };

    class Is_one
      : public CGAL::cpp98::unary_function< Type, Boolean > {
      public:
        Boolean operator()( const Type& x ) const {
          return INTERN_INTERVAL_NT::is_one( x );
        }
    };

    class Square
      : public CGAL::cpp98::unary_function< Type, Type > {
      public:
        Type operator()( const Type& x ) const {
          return INTERN_INTERVAL_NT::square( x );
        }
    };

    class Sqrt
      : public CGAL::cpp98::unary_function< Type, Type > {
      public:
        Type operator()( const Type& x ) const {
          return INTERN_INTERVAL_NT::sqrt( x );
        }
    };

    struct Is_square
        :public CGAL::cpp98::binary_function<Interval_nt<B>,Interval_nt<B>&,Boolean >
    {
        Boolean operator()(const Interval_nt<B>& x) const {
            return INTERN_INTERVAL_NT::is_positive( x );
        }

        Boolean operator()(
                const Interval_nt<B>& x,
                Interval_nt<B>      & result) const {
            Boolean is_positive = INTERN_INTERVAL_NT::is_positive( x );
            if ( is_positive.inf() == true ){
                typename Algebraic_structure_traits<Interval_nt<B> >::Sqrt sqrt;
                result = sqrt(x);
            }else{
                typename Real_embeddable_traits<Interval_nt<B> >::Abs  abs;
                typename Algebraic_structure_traits<Interval_nt<B> >::Sqrt sqrt;
                result = sqrt(abs(x));
            }
            return is_positive;
        }
    };

  class Divides
    : public CGAL::cpp98::binary_function< Type, Type, Boolean > {
  public:
    Boolean operator()( const Type& x, const Type&) const {
      return ! Is_zero()(x);
    } 
    // second operator computing q
    Boolean operator()( const Type& x, const Type& y, Type& q) const {
      if (! Is_zero()(x) )
        q  = y/x ;
      return Boolean(true);
    }
  };
  
};


// COERCION_TRAITS BEGIN
template < class A, class B , int > struct Coercion_traits_for_level;
template < class A, class B, class C> struct Coercion_traits_interval_nt;

template<class A ,bool P >
struct Coercion_traits_for_level<A,Interval_nt<P>,CTL_INTERVAL>
    :public Coercion_traits_interval_nt<A,Interval_nt<P>,
            typename Real_embeddable_traits<A>::Is_real_embeddable>{};

template<class A , bool P>
struct Coercion_traits_for_level<Interval_nt<P>,A,CTL_INTERVAL>
    :public Coercion_traits_for_level<A,Interval_nt<P>, CTL_INTERVAL>{};

template<class A , bool P >
struct Coercion_traits_interval_nt<A, Interval_nt<P>,Tag_false>
    :public Coercion_traits_for_level<A,Interval_nt<P>,0>{};

template<class A , bool P>
struct Coercion_traits_interval_nt<A, Interval_nt<P>, Tag_true>{
    typedef Tag_true Are_explicit_interoperable;
    typedef Tag_false Are_implicit_interoperable;
    typedef Interval_nt<P> Type;
    struct Cast {
        typedef Interval_nt<P> result_type;
        Interval_nt<P> inline operator()(const Interval_nt<P>& x ) const {
            return x;
        }
        Interval_nt<P> inline operator()(const A& x ) const {
            return typename Real_embeddable_traits<A>::To_interval()(x);
        }
    };
};

// COERCION_TRAITS END

template< bool B >
class Interval_traits< Interval_nt<B> >
  : public internal::Interval_traits_base< Interval_nt<B> >  {
public: 
  typedef Interval_traits<Interval_nt<B> > Self; 
  typedef Interval_nt<B> Interval; 
  typedef double Bound; 
  typedef CGAL::Tag_false With_empty_interval; 
  typedef CGAL::Tag_true  Is_interval; 

 struct Construct :public CGAL::cpp98::binary_function<Bound,Bound,Interval>{
    Interval operator()( const Bound& l,const Bound& r) const {
      CGAL_precondition( l < r ); 
      return Interval(l,r);
    }
  };

  struct Lower :public CGAL::cpp98::unary_function<Interval,Bound>{
    Bound operator()( const Interval& a ) const {
      return a.inf();
    }
  };

  struct Upper :public CGAL::cpp98::unary_function<Interval,Bound>{
    Bound operator()( const Interval& a ) const {
      return a.sup();
    }
  };

  struct Width :public CGAL::cpp98::unary_function<Interval,Bound>{
    Bound operator()( const Interval& a ) const {
      return width(a); 
    }
  };

  struct Median :public CGAL::cpp98::unary_function<Interval,Bound>{
    Bound operator()( const Interval& a ) const {
      return (Lower()(a)+Upper()(a))/2.0;
    }
  };
    
  struct Norm :public CGAL::cpp98::unary_function<Interval,Bound>{
    Bound operator()( const Interval& a ) const {
      return magnitude(a);
    }
  };

  struct Singleton :public CGAL::cpp98::unary_function<Interval,bool>{
    bool operator()( const Interval& a ) const {
      return Lower()(a) == Upper()(a);
    }
  };

  struct Zero_in :public CGAL::cpp98::unary_function<Interval,bool>{
    bool operator()( const Interval& a ) const {
      return Lower()(a) <= 0  &&  0 <= Upper()(a);
    }
  };

  struct In :public CGAL::cpp98::binary_function<Bound,Interval,bool>{
    bool operator()( Bound x, const Interval& a ) const {
      return Lower()(a) <= x && x <= Upper()(a);
    }
  };

  struct Equal :public CGAL::cpp98::binary_function<Interval,Interval,bool>{
    bool operator()( const Interval& a, const Interval& b ) const {
      return a.is_same(b);
    }
  };
    
  struct Overlap :public CGAL::cpp98::binary_function<Interval,Interval,bool>{
    bool operator()( const Interval& a, const Interval& b ) const {
      return a.do_overlap(b);
    }
  };
    
  struct Subset :public CGAL::cpp98::binary_function<Interval,Interval,bool>{
    bool operator()( const Interval& a, const Interval& b ) const {
      return Lower()(b) <= Lower()(a) && Upper()(a) <= Upper()(b) ;  
    }
  };
    
  struct Proper_subset :public CGAL::cpp98::binary_function<Interval,Interval,bool>{
    bool operator()( const Interval& a, const Interval& b ) const {
      return Subset()(a,b) && ! Equal()(a,b); 
    }
  };
    
  struct Hull :public CGAL::cpp98::binary_function<Interval,Interval,Interval>{
    Interval operator()( const Interval& a, const Interval& b ) const {
      BOOST_USING_STD_MAX();
      BOOST_USING_STD_MIN();
      return Interval( 
          std::make_pair(
              min BOOST_PREVENT_MACRO_SUBSTITUTION (Lower()(a),b.inf()), 
              max BOOST_PREVENT_MACRO_SUBSTITUTION (Upper()(a),b.sup())));
    }
  };
    
  
//  struct Empty is Null_functor 
  
  struct Intersection :public CGAL::cpp98::binary_function<Interval,Interval,Interval>{
    Interval operator()( const Interval& a, const Interval& b ) const {
      BOOST_USING_STD_MAX();
      BOOST_USING_STD_MIN();
      Bound l(max BOOST_PREVENT_MACRO_SUBSTITUTION (Lower()(a),Lower()(b)));
      Bound u(min BOOST_PREVENT_MACRO_SUBSTITUTION (Upper()(a),Upper()(b)));
      if(u < l ) throw Exception_intersection_is_empty();
      return Construct()(l,u);
    }
  };
};

} //namespace CGAL

namespace Eigen {
  template<class> struct NumTraits;
  template<bool b> struct NumTraits<CGAL::Interval_nt<b> >
  {
    typedef CGAL::Interval_nt<b> Real;
    typedef CGAL::Interval_nt<b> NonInteger;
    typedef CGAL::Interval_nt<b> Nested;
    typedef double Literal;

    static inline Real epsilon() { return 0; }
    static inline Real dummy_precision() { return 0; }

    // Costs could depend on b.
    enum {
      IsInteger = 0,
      IsSigned = 1,
      IsComplex = 0,
      RequireInitialization = 0,
      ReadCost = 2,
      AddCost = 2,
      MulCost = 10
    };
  };

  namespace internal {
    template<class> struct significant_decimals_impl;
    template<bool b>
      struct significant_decimals_impl<CGAL::Interval_nt<b> >
      : significant_decimals_impl<typename CGAL::Interval_nt<b>::value_type> { };
  }
}

#endif // CGAL_INTERVAL_NT_H