gistfile1.txt

Was writing a tuple class for fun.

    template <typename... Ts>
    class tuple {
        template <typename T>
        T& get();
      
        template <typename T>
        T const& get() const;
    };
    
One issue here is the following line(s) of code:

    tuple<A, B> get_tuple();
    
    A a = get_tuple().get<A>();
    
would result in an unnecessary copy of A, because even though `get_tuple` returns an rvalue, `get<A>` returns a const ref.

This is not only inefficient, but would break if A was non-copyable.

One way to fix this with a rvalue ref qualified version of get:

    template <typename... Ts>
    class tuple {
        template <typename T>
        T& get() &;
        
        template <typename T>
        T&& get() &&;
      
        template <typename T>
        T const& get() const &;
    };
    
Tada.