/* D02BJ_P0W_F C++ Header Example Program.
 *
 * Copyright 2020 Numerical Algorithms Group.
 *
 * Mark 27.1, 2020.
 *
 */

#include <nag.h>
#include <nagad.h>
#include <math.h>
#include <stdio.h>
#include <iostream>
using namespace std;

#ifdef __cplusplus
extern "C"
{
#endif
  static void NAG_CALL fcn(void * &ad_handle, const double &x, const double y[],
                           double f[], Integer iuser [], double ruser[]);
  static void NAG_CALL g(void * &ad_handle, const double &x, const double y[],
                         double &retval, Integer iuser [], double ruser[]);
#ifdef __cplusplus
}
#endif

int main(void)
{
  int               exit_status = 0;
  const Integer     n = 3;

  cout << "D02BJ_P0W_F C++ Header Example Program Results\n\n";

  Integer           iw, iuser[1];
  double            pi, tol, x, xinit, xend, ruser[2];
  double            *y = 0, *w = 0;

  iw = 20*n;
  w = new double [iw];
  y = new double [n];

  xinit = 0.0;
  xend = 10.0;
  pi = nag_math_pi;
  
  cout << "\n\nCase: no intermediate output, root-finding\n";
  tol = 1.0e-5;
  cout << "\n  Calculation with tol = " << tol << endl;

  x = xinit;
  y[0] = 0.5;
  y[1] = 0.5;
  y[2] = pi / 5.0;

  const double alpha = -0.032;
  const double beta = -0.02;
  ruser[0] = alpha;
  ruser[1] = beta;

  Integer ifail = 0;
  void    *ad_handle = 0;
  d02bj_p0w_f_(ad_handle,x,xend,n,y,fcn,tol,"D", d02bj_p0w_x_, g,
               w,iuser,ruser,ifail,1);

  cout.setf(ios::fixed);
  cout.setf(ios::right);
  cout.precision(3);
  cout << "\n  Root of Y(1) = 0.0 at ";
  cout.width(5); cout << x << endl;
  cout << "\n  Solution is  ";
  cout.precision(4);
  for (int i = 0; i < 3; ++i) {
    cout.width(10); cout << y[i];
  }
  cout << endl;

  delete [] w;
  delete [] y;
  return exit_status;
}

static void NAG_CALL fcn(void * &ad_handle, const double &x, const double y[],
                         double f[], Integer iuser [], double ruser[])
{
  double alpha, beta;
  alpha = ruser[0];
  beta = ruser[1];

  f[0] = tan(y[2]);
  f[1] = alpha*tan(y[2])/y[1] + beta*y[1]/cos(y[2]);
  f[2] = alpha/(y[1]*y[1]);
}

static void NAG_CALL g(void * &ad_handle, const double &x, const double y[],
                       double &retval, Integer iuser [], double ruser[])
{
  retval = y[0];
}