constexpr example from "Effective Modern C++" by Scott Meyers, Item 15

CppUG_constexpr.cpp

#include <array>
#include <iostream>

#if __cplusplus > 201103L
constexpr int pow(int base, int exp) noexcept
{
    auto result = 1;
    for (int i = 0; i < exp; ++ i) {
        result *= base;
    }
    return result;
}
#else
constexpr int pow(int base, int exp) noexcept
{
    return (exp == 0 ? 1 : base * pow(base, exp -1));
}
#endif  

int main()
{
    // We need to store all possible combinations of n values with 3 states
    constexpr auto n = 5; // n is 5
    std::array<int, pow(3, n)> results;

    std::cout << results.size() << '\n';
}