NAG Library Manual, Mark 27.2
```/* G01FE_A1W_F C++ Header Example Program.
*
* Copyright 2021 Numerical Algorithms Group.
* Mark 27.2, 2021.
*/

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

int main(void)
{
int exit_status = 0;

cout << "G01FE_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 << " Deviates and derivatives\n\n";
cout << "     p           a           b          x";
cout << "       dx/dp       dx/da          dx/db\n";
cout.setf(ios::scientific, ios::floatfield);
cout.setf(ios::right);
cout.precision(4);

// Loop over x values
tol = 0.0;
for (Integer i = 0; i < n; ++i)
{
// Read next p, a and b
double pr, ar, br;
cin >> pr >> ar >> br;

p = pr;
a = ar;
b = br;

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

ifail = 0;

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

double dxdp, dxda, dxdb;
dxdp = dco::derivative(p);
dxda = dco::derivative(a);
dxdb = dco::derivative(b);

cout.width(12);
cout << dco::value(p);
cout.width(12);
cout << dco::value(a);
cout.width(12);
cout << dco::value(b);
cout.width(12);
cout << dco::value(x);
cout.width(12);
cout << dxdp;
cout.width(12);
cout << dxda;
cout.width(12);
cout << dxdb << endl;
}

// Remove computational data object and tape
ifail = 0;