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

#include <nag.h>
#include <nagx04.h>
#include <stdio.h>
#include <math.h>
#include <nag_stdlib.h>
#include <nagc02.h>

int main(int argc, char *argv[])
{
  FILE        *fpin, *fpout;

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

  INIT_FAIL(fail);

  /* Check for command-line IO options */
  fpin = nag_example_file_io(argc, argv, "-data", NULL);
  fpout = nag_example_file_io(argc, argv, "-results", NULL);
  fprintf(fpout, "nag_zeros_real_poly (c02agc) Example Program Results\n");
  /* Skip heading in data file */
  fscanf(fpin, "%*[^\n]");
  fscanf(fpin, "%ld", &n);
  if (n > 0)
    {
      scale = Nag_TRUE;
      if (!(a = NAG_ALLOC(n+1, double)) ||
          !(z = NAG_ALLOC(n, Complex)))
        {
          fprintf(fpout, "Allocation failure\n");
          exit_status = -1;
          goto END;
        }
    }
  else
    {
      fprintf(fpout, "Invalid n.\n");
      exit_status = 1;
      return exit_status;
    }

  for (i = 0; i <= n; i++)
    fscanf(fpin, "%lf", &a[i]);
  fprintf(fpout, "\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)
    {
      fprintf(fpout, "Error from nag_zeros_real_poly (c02agc).\n%s\n",
              fail.message);
      exit_status = 1;
      goto END;
    }

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