/**
* @author Ayoub Chouak (@ntauth)
* @website http://chouak.me
* @note This requires a C++17-compliant compiler (ex. MSVC14, Clang5)
*/

#include <optional>
#include <iostream>
#include <string>
#include <chrono>

template <typename U>
std::ostream& operator<<(std::ostream& os, std::optional<U> nullable) {
    if (nullable.has_value())
        os << nullable.value();
    return os;
}

int main(int argc, char** argv)
{
    std::optional<int> int_n;
    std::optional<std::string> string_n;
    std::optional<std::string> string_n_{ "I have a value!" };
	
    std::cout << int_n << string_n << string_n_ << std::endl;
    std::cin.get();
}