#include <array>
#include <vector>
#include <map>
#include <iostream>
#include <functional>


template<class ... Arguments>
class Callback
{
    using Function = std::function<void(Arguments ...)>;
    using FunctionPtr = std::shared_ptr<Function>;
    using Functions = std::vector<FunctionPtr>;

public:
    FunctionPtr addListener(Function f) {
        FunctionPtr fp = std::make_shared<Function>(f);
        _functions.push_back(fp);
        return fp;
    }

    void removeListener(FunctionPtr fp) {
        _functions.erase(std::find(_functions.begin(), _functions.end(), fp));
    }

    void operator()(Arguments ... args) const {
        for (auto& f : _functions)
            f.get()->operator()(args ...);
    }

private:
    Functions _functions;
};


void test(int i) {
    std::cout << "test: " << i << std::endl;
}

int main()
{
    Callback<int> callback;

    callback.addListener([](int i) {
        std::cout << "Listener 1 -> Input is " << i << std::endl;
        });

    auto id = callback.addListener([](int i) {
        std::cout << "Listener 2 -> Input is " << i << std::endl;
        });

    callback.addListener([](int i) {
        std::cout << "Listener 3 -> Input is " << i << std::endl;
        });

    callback.addListener(test); 

    callback.removeListener(id);

    callback(71);
}