NAG Library Manual, Mark 28.5
```/* D01RK_P0W_F C++ Header Example Program.
*
* Copyright 2022 Numerical Algorithms Group.
* Mark 28.5, 2022.
*/

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

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

cout << "D01RK_P0W_F C++ Header Example Program Results\n\n";

Integer key = 6;
double  pi  = X01AAC;
double  a, b, epsabs, epsrel;
a      = 0.0;
b      = 2.0 * pi;
epsabs = 0.0;
epsrel = 1.0e-4;

Integer  maxsub = 20;
Integer  lrinfo = 80;
Integer  liinfo = 20;
double * rinfo  = 0;
Integer *iinfo  = 0;

rinfo = new double[lrinfo];
iinfo = new Integer[liinfo];

double            result, abserr, ruser[2];
Integer           iuser[1];
iuser[0]                 = 0;
ruser[0]                 = 30.0;
ruser[1]                 = 1.0;

const double *x,
const Integer &         nx,
double *fv,
Integer &               iflag)
{
// dco/c++ used here to perform AD of the following
for (int i = 0; i < nx; i++)
{
fv[i] = x[i] * sin(ruser[0] * x[i]) * cos(ruser[1] * x[i]);
}
};
// Call the passive routine
Integer ifail = -1;
abserr, rinfo, iinfo, ifail);
if (ifail < 0)
{
cout << "\n ** nag::ad::d01rk failed error exit ifail = " << ifail << endl;
goto END;
}
// Print inputs and primal outputs.
cout << "\n lower limit of integration (a) = " << a << endl;
cout << " upper limit of integration (b) = " << b << endl;
cout << " choice of Gaussian rule (key)  = " << key << endl;
cout << " absolute accuracy requested    = " << epsabs << endl;
cout << " relative accuracy requested    = " << epsrel << endl;
cout << " maximum number of subintervals = " << maxsub << endl;
cout.setf(ios::scientific, ios::floatfield);
cout.precision(4);
if (ifail >= 0)
{
cout << "\n approximation to the integral  : " << result << endl;
cout << " estimate of the absolute error : " << abserr << endl;
cout << " number of function evaluations : " << iinfo[0] << endl;
}

END:

delete[] rinfo;
delete[] iinfo;
return exit_status;
}
```