NAG Library Manual, Mark 28.6
```/* G01HA_A1W_F C++ Header Example Program.
*
* Copyright 2022 Numerical Algorithms Group.
* Mark 28.6, 2022.
*/

#include <dco.hpp>
#include <iostream>
#include <nag.h>
#include <stdio.h>
#include <string>
using namespace std;

int main()
{
int exit_status = 0;

// Input and output variables

cout << "G01HA_A1W_F C++ Header Example Program Results\n\n";
// Skip heading in data file
string mystr;
getline(cin, mystr);

// Read number of x values
Integer n;
cin >> n;

dco::ga1s<double>::global_tape = dco::ga1s<double>::tape_t::create();

// Create AD configuration data object
Integer           ifail = 0;

cout << "Lower tail significance levels and derivatives\n\n";
cout << "       x           y         rho          p";
cout << "         dp/dx       dp/dy      dp/drho\n";
cout.setf(ios::scientific, ios::floatfield);
cout.setf(ios::right);
cout.precision(4);

// Loop over x values
for (Integer i = 0; i < n; ++i)
{
// Read next x, y and rho
double xr, yr, rhor;
cin >> xr >> yr >> rhor;
x   = xr;
y   = yr;
rho = rhor;

// Register x, i.e. differentiate w.r.t. x
dco::ga1s<double>::global_tape->register_variable(x);
dco::ga1s<double>::global_tape->register_variable(y);
dco::ga1s<double>::global_tape->register_variable(rho);

ifail = 0;

double inc = 1.0;
dco::derivative(p) += inc;
ifail                                              = 0;
dco::ga1s<double>::global_tape->sparse_interpret() = true;

// Get derivative, dydx and output values
double dpdx, dpdy, dpdr;
dpdx = dco::derivative(x);
dpdy = dco::derivative(y);
dpdr = dco::derivative(rho);

cout.width(12);
cout << dco::value(x);
cout.width(12);
cout << dco::value(y);
cout.width(12);
cout << dco::value(rho);
cout.width(12);
cout << dco::value(p);
cout.width(12);
cout << dpdx;
cout.width(12);
cout << dpdy;
cout.width(12);
cout << dpdr << endl;
}

dco::ga1s<double>::tape_t::remove(dco::ga1s<double>::global_tape);

return exit_status;
}
```