/* nag_interval_zero_cont_func (c05avc) Example Program.
 *
 * Copyright 2006 Numerical Algorithms Group.
 *
 * Mark 9, 2009.
 */

#include <nag.h>
#include <nagx04.h>
#include <stdio.h>
#include <nag_stdlib.h>
#include <math.h>
#include <nagc05.h>

int main(int argc, char *argv[])
{
  FILE     *fpout;
  /* Scalars */
  Integer  exit_status = 0;
  double   boundl, boundu, fx, h, x, y;
  Integer  ind;
  /* Arrays */
  double   c[11];
  NagError fail;

  INIT_FAIL(fail);

  /* Check for command-line IO options */
  fpout = nag_example_file_io(argc, argv, "-results", NULL);
  fprintf(fpout,
          "nag_interval_zero_cont_func (c05avc) Example Program Results\n");

  x = 3.0;
  h = 0.1;
  boundl = 0.0;
  boundu = 4.0;
  ind = 1;
  /* nag_interval_zero_cont_func (c05avc).
   * Locates an interval containing a simple zero of a continuous
   * function using binary search and reverse communication.
   */
  while (ind != 0)
    {
      nag_interval_zero_cont_func(&x, fx, &h, boundl, boundu, &y, c, &ind,
                                  &fail);

      if (ind != 0)
        {
          fx = pow(x, 2) - 3.0*x + 2.0;
        }
    }

  if (fail.code == NE_NOERROR)
    {
      fprintf(fpout, "Interval containing root is [x,y], where\n");
      fprintf(fpout, "x = %12.4f, y = %12.4f\n", x, y);
      fprintf(fpout, "Values of f at x and y are\n");
      fprintf(fpout, "f(x) = %12.2f, f(y) = %12.2f\n", fx, c[0]);
    }
  else
    {
      fprintf(fpout, "%s\n", fail.message);
      exit_status = 1;
      goto END;
    }

 END:
  if (fpout != stdout) fclose(fpout);
  return exit_status;
}