/* nag_zeros_real_poly (c02agc) Example Program.
 *
 * Copyright 1991 Numerical Algorithms Group.
 *
 * Mark 2, 1991.
 *
 * Mark 8 revised, 2004.
 */

#include <nag.h>
#include <stdio.h>
#include <math.h>
#include <nag_stdlib.h>
#include <nagc02.h>

int main(void)
{

  Nag_Boolean scale;
  Complex     *z = 0;
  Integer     exit_status = 0, i, n, nroot;
  NagError    fail;
  double      *a = 0;

  INIT_FAIL(fail);

  printf("nag_zeros_real_poly (c02agc) Example Program Results\n");
  /* Skip heading in data file */
  scanf("%*[^\n]");
  scanf("%ld", &n);
  if (n > 0)
    {
      scale = Nag_TRUE;
      if (!(a = NAG_ALLOC(n+1, double)) ||
          !(z = NAG_ALLOC(n, Complex)))
        {
          printf("Allocation failure\n");
          exit_status = -1;
          goto END;
        }
    }
  else
    {
      printf("Invalid n.\n");
      exit_status = 1;
      return exit_status;
    }

  for (i = 0; i <= n; i++)
    scanf("%lf", &a[i]);
  printf("\nDegree of polynomial = %4ld\n\n", n);

  /* nag_zeros_real_poly (c02agc).
   * Zeros of a polynomial with real coefficients
   */
  nag_zeros_real_poly(n, a, scale, z, &fail);
  if (fail.code != NE_NOERROR)
    {
      printf("Error from nag_zeros_real_poly (c02agc).\n%s\n",
              fail.message);
      exit_status = 1;
      goto END;
    }

  printf("Roots of polynomial\n\n");
  nroot = 1;
  while (nroot <= n)
    {
      if (z[nroot-1].im == 0.0)
        {
          printf("z = %13.4e\n", z[nroot-1].re);
          nroot += 1;
        }
      else
        {
          printf("z = %13.4e   +/- %14.4e\n", z[nroot-1].re,
                  fabs(z[nroot-1].im));
          nroot += 2;
        }
    }
 END:
  if (a) NAG_FREE(a);
  if (z) NAG_FREE(z);
  return exit_status;
}