/* poly/companion.c

 * 

 * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 Brian Gough

 * 

 * This program 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 3 of the License, or (at

 * your option) any later version.

 * 

 * This program 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 this program; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

 */

static void set_companion_matrix (const double *a, size_t n, double *m);

static void

set_companion_matrix (const double *a, size_t nc, double *m)

{

  size_t i, j;

  for (i = 0; i < nc; i++)

    for (j = 0; j < nc; j++)

      MAT (m, i, j, nc) = 0.0;

  for (i = 1; i < nc; i++)

    MAT (m, i, i - 1, nc) = 1.0;

  for (i = 0; i < nc; i++)

    MAT (m, i, nc - 1, nc) = -a[i] / a[nc];

}