NAG Library Manual, Mark 28.6
Interfaces:  FL   CL   CPP   AD
```#include "dco.hpp"
/* G01EA_A1W_F C++ Header Example Program.
*
* Copyright 2022 Numerical Algorithms Group.
* Mark 28.6, 2022.
*/

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

int main()
{
int exit_status = 0;

// Input and output variables

cout << "G01EA_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;

// Create AD tape
dco::ga1s<double>::global_tape = dco::ga1s<double>::tape_t::create();

// Create AD configuration data object

cout << "Two tail significance levels and derivatives\n\n";
cout << "       x           p         dp/dx\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
double xr;
cin >> xr;
x = xr;
// Register x, i.e. differentiate w.r.t. x
dco::ga1s<double>::global_tape->register_variable(x);

// Call NAG AD Routine
Integer ifail = 0;

// Reset adjoints, increment y, and evaluate adjoint of y w.r.t. x
double inc = 1.0;
dco::derivative(p) += inc;
dco::ga1s<double>::global_tape->sparse_interpret() = true;

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

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

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

return exit_status;
}
```