NAG Library Manual, Mark 27.3
```/* E01AA_T1W_F C++ Header Example Program.
*
* Copyright 2021 Numerical Algorithms Group.
* Mark 27.3, 2021.
*/

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

int main()
{
// Scalars
int exit_status = 0;

cout << "E01AA_T1W_F C++ Header Example Program Results\n\n";

// Skip first line of data file
string mystr;
getline(cin, mystr);
// Read number of data points
Integer n;
cin >> n;

// Allocate arrays for data and interpolant
nagad_t1w_w_rtype x, *a = 0, *b = 0, *c = 0;
double            xr, fx, *ar = 0, *br = 0, *dx = 0;
Integer           n1, n2;
n1 = n + 1;
n2 = n * (n + 1) / 2;
ar = new double[n1];
br = new double[n1];
dx = new double[n1];

cin >> xr;

for (int i = 0; i < n1; i++)
{
cin >> ar[i];
}
for (int i = 0; i < n1; i++)
{
cin >> br[i];
}

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

for (int i = 0; i < n1; ++i)
{
x = xr;
for (int j = 0; j < n1; j++)
{
a[j] = ar[j];
b[j] = br[j];
}

double inc            = 1.0;
dco::derivative(a[i]) = inc;

ifail = 0;

if (i == 0)
{
fx = dco::value(c[n2 - 1]);
}

double zero           = 0.0;
dco::derivative(a[i]) = zero;

dx[i] = dco::derivative(c[n2 - 1]);
}

cout.setf(ios::scientific, ios::floatfield);
cout.precision(5);
cout << "\n Interpolation point = ";
cout.width(12);
cout << xr << endl;
cout << "\n Function value at interpolation point = ";
cout.width(12);
cout << fx << endl;

cout << "\n Derivatives calculated: First order tangents\n";
cout << " Computational mode    : algorithmic\n";

// Get derivatives
cout << "\n Derivatives of fitted value w.r.t. x values:\n";
cout << "  j         d/da(j)\n";
for (int j = 0; j < n1; j++)
{
cout.width(3);
cout << j + 1 << "     ";
cout.width(12);
cout << dx[j] << endl;
}

delete[] ar;
delete[] br;
delete[] dx;
delete[] a;
delete[] b;
delete[] c;
return exit_status;
}
```