C++ Insights

Source:

#include <iostream>
#include <functional>

struct Foo {
    void operator()() {
        std::cout << "Foo@" << __func__ << ":" << __LINE__ << std::endl;
    }
};

struct Bar {
    using fun_t = void(*)();
    static void invoke() {
        std::cout << "Bar@" << __func__ << ":" << __LINE__ << std::endl;
    }
    operator fun_t() {
        return invoke;
    }
};

struct FooBar {
    using fun_t = void(*)();
    static void invoke() {
        std::cout << "FooBar@" << __func__ << ":" << __LINE__ << std::endl;
    }
    operator fun_t() {
        return invoke;
    }
    void operator()() {
        std::cout << "FooBar@" << __func__ << ":" << __LINE__ << std::endl;
    }
    void operator()(int) {
        std::cout << "FooBar@" << __func__ << ":" << __LINE__ << std::endl;
    }
};

int main(int argc, char **argv) {
    using fun_t = void(*)();
    Foo foo;
    foo();
    Bar bar;
    bar();
    FooBar fb;
    fb();
    fun_t f = fb;
    f();
    std::function<void()> func_c = f;
    f();
    std::function<void()> func = fb;
    func();
    std::function<void(int)> func_int = fb;
    func_int(0);
    return 0;
}

Source:

Insight:

Console: