---

matrix2x2.cpp

//$Header: /home/ben/Mapper/c++/RCS/matrix2x2.cpp,v 6.4 2002/07/06 17:41:50 ben Exp $
// Copyright Benedict Adamson 2002.
// This file is part of Mapper.

// Mapper is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.

// Mapper is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Mapper; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

#include "matrix2x2.h"



//matrix2x2 operator* (
//   const matrix2x2 &a,
//   const matrix2x2 &b
//   )
//{
//   return matrix2x2(
//      a.row0.x * b.row0.x + a.row0.y * b.row1.x,
//      a.row0.x * b.row0.y + a.row0.y * b.row1.y,
//      a.row1.x * b.row0.x + a.row1.y * b.row1.x,
//      a.row1.x * b.row0.y + a.row1.y * b.row1.y
//      );
//}



vector2 matrix2x2::solve(
   const matrix2x2 &M,
   const vector2 &y
   )
{
   //returns the x, such that M*x == y;
   const matrix2x2 Mi(
      M[1][1], -M[0][1],
      -M[1][0], M[0][0]
      );
   const double d = 1.0/det( M );
   return Mi * (d * y);
}

---