mirror of https://github.com/CGAL/cgal
75 lines
2.2 KiB
C++
75 lines
2.2 KiB
C++
// Copyright (c) 2007-2008 Inria Lorraine (France). 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; version 2.1 of the License.
|
|
// See the file LICENSE.LGPL 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.
|
|
//
|
|
// $URL$
|
|
// $Id$
|
|
//
|
|
// Author: Luis Peñaranda <luis.penaranda@loria.fr>
|
|
|
|
#ifndef CGAL_RS__INVERSE_H
|
|
#define CGAL_RS__INVERSE_H
|
|
|
|
#ifdef _MSC_VER
|
|
# define _s64 __int64
|
|
# define _u64 unsigned __int64
|
|
# define _u32 unsigned __int32
|
|
#else
|
|
# include <stdint.h>
|
|
# define _s64 int64_t
|
|
# define _u64 uint64_t
|
|
# define _u32 uint32_t
|
|
#endif
|
|
|
|
#define n_(A) (A<0?-A:A)
|
|
//#define u_(A) (A<0?-1:1)
|
|
#define u_(A,C) (A<0?(C<0?1:-1):(C<0?-1:1))
|
|
|
|
namespace CGAL{
|
|
namespace RS_MGCD{
|
|
|
|
class Inverse{
|
|
|
|
protected:
|
|
// given a and b, returns s such that gcd(a,b)=s*a+t*b (GCL, page 36)
|
|
// s*a+t*q=1 => s is the inverse of a, mod q (pafe 173)
|
|
static _s64 eea_s(_u32 a,_u32 b){
|
|
_s64 c1,d1,r1;//,c2,d2,r2,t,s;
|
|
_u32 r,c,d;//,q;
|
|
// a and b are positive, so a=n_(a) and b=n_(b)
|
|
//c=n_(a); d=n_(b);
|
|
c=a; d=b;
|
|
c1=1; d1=0;
|
|
//c2=0; d2=1;
|
|
while(d){
|
|
//q=c/d;
|
|
r=c%d;
|
|
r1=c1-d1*(c/d); //r2=c2-d2*q;
|
|
c=d; c1=d1; //c2=d2;
|
|
d=r; d1=r1; //d2=r2;
|
|
}
|
|
// gcd(a,b) is n_(c)
|
|
//t=c2/(_u(b)*u_(c));
|
|
// a and c are always positive, so s=c1/u_(a,c) equals c1
|
|
//s=c1/u_(a,c);
|
|
//return s;
|
|
return c1;
|
|
};
|
|
}; // class Inverse
|
|
|
|
} // namespace RS_MGCD
|
|
} // namespace CGAL
|
|
|
|
#endif // CGAL_RS__INVERSE_H
|
|
|
|
// vim: tabstop=4: softtabstop=4: smarttab: shiftwidth=4: expandtab
|