/* nag_zero_cont_func_brent (c05ayc) Example Program.
 *
 * Copyright 2011 Numerical Algorithms Group.
 *
 * Mark 23, 2011.
 */

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

#ifdef __cplusplus
extern "C" {
#endif
static double NAG_CALL f(double x, Nag_Comm *comm);
#ifdef __cplusplus
}
#endif

int main(void)
{
  Integer  exit_status = 0;
  double   a, b;
  double   x, eta, eps;
  NagError fail;
  Nag_Comm comm;

  INIT_FAIL(fail);

  printf("nag_zero_cont_func_brent (c05ayc) Example Program Results\n");

  a = 0.0;
  b = 1.0;
  eps = 1e-05;
  eta = 0.0;

  /* nag_zero_cont_func_brent (c05ayc).
   * Zero of a continuous function using Brent's algorithm
   */
  nag_zero_cont_func_brent(a, b, eps, eta, f, &x, &comm, &fail);
  if (fail.code == NE_NOERROR)
    {
      printf("Zero = %12.5f\n", x);
    }
  else
    {
      printf("%s\n", fail.message);
      if (fail.code == NE_TOO_SMALL ||
          fail.code == NE_PROBABLE_POLE)
        printf("Final point = %12.5f\n", x);
      exit_status = 1;
      goto END;
    }

 END:
  return exit_status;
}

static double NAG_CALL f(double x, Nag_Comm *comm)
{
  return exp(-x)-x;
}