NAG Library Manual, Mark 28.4
```/* D01FB_P0W_F C++ Header Example Program.
*
* Copyright 2022 Numerical Algorithms Group.
* Mark 28.4, 2022.
*/

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

int main()
{
// Scalars
int     exit_status = 0;
Integer ndim        = 4;

cout << "D01FB_P0W_F C++ Header Example Program Results\n\n";

// Allocate memory
Integer *nptvec = 0;
double * abscis = 0, *weight = 0;
Integer  lwa = 0;

nptvec = new Integer[ndim];
for (int i = 0; i < ndim; i++)
{
nptvec[i] = 4;
lwa       = lwa + nptvec[i];
}
abscis = new double[lwa];
weight = new double[lwa];

// Evaluate primal weights and abscisae in each dimension
int j = 0;
for (int i = 0; i < ndim; i++)
{

Integer ifail = 0, quadtype = 0;
double  a, b;
switch (i)
{
case 0:
a        = 1.0;
b        = 2.0;
break;
case 1:
a        = 0.0;
b        = 2.0;
break;
case 2:
a        = 0.0;
b        = 0.5;
break;
case 3:
a        = 1.0;
b        = 2.0;
break;
}
ifail);
j = j + nptvec[i];
}

// Call the passive routine
Integer ifail = 0;
double  ans;
const Integer &         ndim,
const double *x,
double &     ret)
{
double            p1 = 6.0, p2 = 8.0;
double r1, r2;
// Split the following function into manageable chunks
// ret = (pow(x[0]*x[1]*x[2],p1)/pow(x[3]+2.0,p2))*
//       exp(-2.0*x[1]-0.5*x[2]*x[2]);
r1  = x[2] * x[2];
r1  = 0.5 * r1;
r2  = -2.0 * x[1];
r1  = r2 - r1;
ret = exp(r1);
r1  = x[0] * x[1] * x[2];
r1  = pow(r1, p1);
r2  = x[3] + 2.0;
r2  = pow(r2, p2);
r2  = r1 / r2;
ret = ret * r2;
};