uncertain_functions_on_signs.h

很多二维 三维几何计算算法 C++ 类库

// Copyright (c) 2003  INRIA Sophia-Antipolis (France).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org); you may redistribute it under
// the terms of the Q Public License version 1.0.
// See the file LICENSE.QPL distributed with CGAL.
//
// 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: svn+ssh://scm.gforge.inria.fr/svn/cgal/branches/CGAL-3.3-branch/Apollonius_graph_2/include/CGAL/Apollonius_graph_2/uncertain/uncertain_functions_on_signs.h $
// $Id: uncertain_functions_on_signs.h 32596 2006-07-18 14:11:07Z mkaravel $
// 
//
// Author(s)     : Menelaos Karavelas <[e-mail]>



#ifndef CGAL_UNCERTAIN_FUNCTIONS_ON_SIGNS_H
#define CGAL_UNCERTAIN_FUNCTIONS_ON_SIGNS_H

#include <CGAL/enum.h>
#include <CGAL/Uncertain.h>

CGAL_BEGIN_NAMESPACE
#if 0
inline
Sign
operator*(const Sign &s1, const Sign &s2)
{
  if ( s1 == ZERO || s2 == ZERO )  return ZERO;
  if ( s1 == s2 )  return POSITIVE;
  return NEGATIVE;
}
#endif

template < class RT >
Uncertain<Sign>
uncertain_sign_a_plus_b_x_sqrt_c(const RT &a, const RT &b, const RT &c)
{
  // computes the sign of quantity: a + b * sqrt(c)

  CGAL_assertion( !(CGAL::is_negative(c)) );

  Uncertain<Sign> sa = CGAL::sign(a);
  if ( is_indeterminate(sa) ) {
    return Uncertain<Sign>::indeterminate();
  }

  Uncertain<Sign> sc = CGAL::sign(c);
  if ( is_indeterminate(sc) ) {
    return Uncertain<Sign>::indeterminate();
  }
  if ( sc == ZERO )  return sa;

  Uncertain<Sign> sb = CGAL::sign(b);
  if ( is_indeterminate(sb) ) {
    return Uncertain<Sign>::indeterminate();
  }
  if ( sa == sb )  return sa;
  if ( sa == ZERO )  return sb;

  Uncertain<Comparison_result> cr =
    CGAL::compare( CGAL::square(a), c * CGAL::square(b) );
  if ( is_indeterminate(cr) ) {
    return Uncertain<Sign>::indeterminate();
  }

  // these casts are ugly; they should go away
  return Sign(Sign(sa) * Comparison_result(cr));
}

#if 0
template < class RT >
Sign
sign_a_x_sqrt_c_plus_b_x_sqrt_d(const RT &a, const RT &b,
				const RT &c, const RT &d)
{
  // computes the sign of quantity: a * sqrt(c) + b * sqrt(d)

  CGAL_assertion( !(CGAL::is_negative(c)) );
  CGAL_assertion( !(CGAL::is_negative(d)) );

  Sign sb = CGAL::sign(b);
  if ( CGAL::sign(d) == ZERO )  return CGAL::sign(a * c);
  if ( CGAL::sign(c) == ZERO )  return sb;

  Sign sa = CGAL::sign(a);
  if ( sa == sb )  return sa;
  if ( sa == ZERO )  return sb;

  return Sign( sa * CGAL::compare( CGAL::square(a) * c,
				   CGAL::square(b) * d )
	       );
}

template < class RT >
Sign
sign_a_plus_b_x_sqrt_e_plus_c_x_sqrt_f(const RT &a, const RT &b,
				       const RT &c, const RT &e,
				       const RT &f)
{
  // computes the sign of quantity: a + b * sqrt(e) + c * sqrt(f)
  
  CGAL_assertion( !(CGAL::is_negative(e)) );
  CGAL_assertion( !(CGAL::is_negative(f)) );

  Sign s_a_plus_b_x_sqrt_e = sign_a_plus_b_x_sqrt_c(a, b, e);
  if ( CGAL::sign(f) == ZERO )  return s_a_plus_b_x_sqrt_e;

  Sign sc = CGAL::sign(c);
  if ( s_a_plus_b_x_sqrt_e == sc )  return sc;
  if ( s_a_plus_b_x_sqrt_e == ZERO )  return sc;

  return s_a_plus_b_x_sqrt_e * 
    sign_a_plus_b_x_sqrt_c(CGAL::square(a) + CGAL::square(b) * e
			   - CGAL::square(c) * f,
			   RT(2) * a * b, e);
}

template < class RT >
Sign
sign_a_plus_b_x_sqrt_e_plus_c_x_sqrt_f_plus_d_sqrt_e_x_f(const RT &a,
							 const RT &b,
							 const RT &c,
							 const RT &d,
							 const RT &e,
							 const RT &f)
{
  // computes the sign of quantity:
  //           a + b * sqrt(e) + c * sqrt(f) + d * sqrt(e * f)
  
  CGAL_assertion( !(CGAL::is_negative(e)) );
  CGAL_assertion( !(CGAL::is_negative(f)) );

  Sign s_a_plus_b_sqrt_e = sign_a_plus_b_x_sqrt_c(a, b, e);
  Sign s_c_plus_d_sqrt_e = sign_a_plus_b_x_sqrt_c(c, d, e);

  if ( s_a_plus_b_sqrt_e == s_c_plus_d_sqrt_e )
    return s_a_plus_b_sqrt_e;

  if ( s_a_plus_b_sqrt_e == ZERO )
    return s_a_plus_b_sqrt_e;

  return s_a_plus_b_sqrt_e *
    sign_a_plus_b_x_sqrt_c(CGAL::square(a) + CGAL::square(b) * e
			   - CGAL::square(c) * f
			   - CGAL::square(d) * e * f,
			   RT(2) * (a * b - c * d * f),
			   e);
}
#endif

CGAL_END_NAMESPACE


#endif // CGAL_UNCERTAIN_FUNCTIONS_ON_SIGNS_H