To define `recursive_power_of_2`

, you can take advantage of
the `power_of_2`

function already provided in
Chapter 20.

Given that `power_of_2`

exists, one way to define
`recursive_power_of_2`

is to hand over the real work to
`power_of_2`

as follows:

```
int recursive_power_of_2 (int n) {
return power_of_2 (n);
}
```

Once you see that you can define `recursive_power_of_2`

in terms of
`power_of_2`

, you are ready to learn how gradually to turn
`recursive_power_of_2`

into a recursive function that does not rely
on `power_of_2`

.