tt() = delete; // make sure it cannot be default constructed

tt(int val): val_(val) {}

tt(const tt& other): val_(other.val_) { std::cout << "tt copy constructor\n"; }

tt(tt&& other): val_(other.val_) { std::cout << "tt move constructor\n"; }

tt& operator=(const tt& other) { val_ = other.val_; std::cout << "tt copy assignment\n"; return *this; }

tt& operator=(tt&& other) { val_ = other.val_; std::cout << "tt move assignment\n"; return *this; }

int get_val() const { return val_; }

int val_;