Here's an example of a C++ function for fast power implemented using recursion:

```
double fastPower(double base, int exponent) {
    if (exponent == 0)
        return 1.0;
    double result = fastPower(base, exponent / 2);
    if (exponent % 2 == 0)
        return result * result;
    else if (exponent > 0)
        return base * result * result;
    else
        return result * result / base;
}
```

This method calculates the result of raising a number (`base`) to a power (`exponent`) using recursion and some math tricks to make it more efficient. It uses the fact that `x^y = (x^(y/2))^2` to split the exponent in half at each recursive call. It also handles negative exponents since `x^-y = 1/(x^y)`.
Scrivere una funzione C++ per l'alimentazione rapida.