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companion.c

/* poly/companion.c
 * 
 * Copyright (C) 1996, 1997, 1998, 1999, 2000 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 2 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];
}

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