mirror of https://github.com/CGAL/cgal
76 lines
2.3 KiB
C++
76 lines
2.3 KiB
C++
// Copyright (c) 2007-2008 Inria Lorraine (France). All rights reserved.
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//
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// This file is part of CGAL (www.cgal.org); you can redistribute it and/or
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// modify it under the terms of the GNU Lesser General Public License as
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// published by the Free Software Foundation; either version 3 of the License,
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// or (at your option) any later version.
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//
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// Licensees holding a valid commercial license may use this file in
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// accordance with the commercial license agreement provided with the software.
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//
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// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
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// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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//
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// $URL$
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// $Id$
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//
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// Author: Luis Peñaranda <luis.penaranda@gmx.com>
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#ifndef CGAL_RS__INVERSE_H
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#define CGAL_RS__INVERSE_H
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#ifdef _MSC_VER
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# define CGALRS_S64 __int64
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# define CGALRS_U64 unsigned __int64
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# define CGALRS_U32 unsigned __int32
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#else
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# include <stdint.h>
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# define CGALRS_S64 int64_t
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# define CGALRS_U64 uint64_t
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# define CGALRS_U32 uint32_t
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#endif
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namespace CGAL{
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namespace RS_MGCD{
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#define CGALRS_N(A) (A<0?-A:A)
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//#define CGALRS_U(A) (A<0?-1:1)
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#define CGALRS_U(A,C) (A<0?(C<0?1:-1):(C<0?-1:1))
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class Inverse{
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protected:
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// given a and b, returns s such that gcd(a,b)=s*a+t*b (GCL, page 36)
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// s*a+t*q=1 => s is the inverse of a, mod q (pafe 173)
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static CGALRS_S64 eea_s(CGALRS_U32 a,CGALRS_U32 b){
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CGALRS_S64 c1,d1,r1;//,c2,d2,r2,t,s;
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CGALRS_U32 r,c,d;//,q;
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// a and b are positive, so a=CGALRS_N(a) and b=CGALRS_N(b)
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//c=CGALRS_N(a); d=CGALRS_N(b);
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c=a; d=b;
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c1=1; d1=0;
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//c2=0; d2=1;
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while(d){
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//q=c/d;
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r=c%d;
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r1=c1-d1*(c/d); //r2=c2-d2*q;
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c=d; c1=d1; //c2=d2;
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d=r; d1=r1; //d2=r2;
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}
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// gcd(a,b) is CGALRS_N(c)
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//t=c2/(CGALRS_U(b)*CGALRS_U(c));
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// a and c are always positive, so s=c1/CGALRS_U(a,c) equals c1
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//s=c1/CGALRS_U(a,c);
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//return s;
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return c1;
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};
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}; // class Inverse
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#undef CGALRS_N
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#undef CGALRS_U
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} // namespace RS_MGCD
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} // namespace CGAL
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#endif // CGAL_RS__INVERSE_H
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