Implementation of 'fast exponentiation' algorithm in C & Python

fast_exponentiation.c

#include <stdint.h>
#include <stdio.h>

double fast_exp(double base, uint64_t power)
{
    double result = 1;
    while (power > 0)
    {
        result *= (power & 1) ? base : 1;
        power >>= 1;
        base *= base;
    }
    return result;
}


/* Entry point used for basic testing */
int main(void)
{
    double base = 3;
    uint64_t power = 4;
    double result = fast_exp(base, power);
    printf("%lf raised to power %llu = %lf\n", base, power, result);

    base = 2;
    power = 5;
    result = fast_exp(base, power);
    printf("%lf raised to power %llu = %lf\n", base, power, result);

    base = 6;
    power = 0;
    result = fast_exp(base, power);
    printf("%lf raised to power %llu = %lf\n", base, power, result);

    return 0;
}

fast_exponentiation.py

from typing import Union


def fast_exp(base: Union[int, float], power: int) -> Union[int, float]:
    """
    Implementation of fast exponentiation for a real `base` raised to
    natural number `power`

    >>> fast_exp(3, 4)
    81
    >>> fast_exp(2.0, 4)
    16.0
    >>> fast_exp(2, 5)
    32
    >>> fast_exp(200, 0)
    1
    >>> fast_exp(2.0, 0)
    1
    """
    result = 1
    while power:
        if power & 1:  # equivalent to `power % 2 == 1`
            result *= base
        power >>= 1  # equivalent to `power //= 2`
        base *= base
    return result