Any way faster than pow() to compute an integer power of 10 in C++?

Question

I know power of 2 can be implemented using << operator. What about power of 10? Like 10^5? Is there any way faster than pow(10,5) in C++? It is a pretty straight-forw

Answer 1

A solution for any base using template meta-programming :

template
struct pow {
    enum { value = E * pow::value };
};

template 
struct pow {
    enum { value = 1 };
};

Then it can be used to generate a lookup-table that can be used at runtime :

template
long long quick_pow(unsigned int n) {
    static long long lookupTable[] = {
        pow::value, pow::value, pow::value,
        pow::value, pow::value, pow::value,
        pow::value, pow::value, pow::value,
        pow::value
    };

    return lookupTable[n];
}

This must be used with correct compiler flags in order to detect the possible overflows.

Usage example :

for(unsigned int n = 0; n < 10; ++n) {
    std::cout << quick_pow<10>(n) << std::endl;
}