On 23/05/2010 21:09, Steven Watanabe wrote:
I'm wondering whether it would be better to use something like
template<class T> struct rv { T* impl; operator const T&() const; };
template<class T> T& unwrap_rv(rv<T>&);
This does not seem to work: template<class T> struct rv_ref { rv_ref(T &t){ ptr = &t; } rv_ref(const T &t){ ptr = &t; } operator const T& () const { return this->get(); } T& get() { return *const_cast<T*>(ptr); } const T& get() const { return *ptr; } private: const T *ptr; }; template<class T> inline rv_ref<T> move(T &t) { return static_cast< rv_ref<T> >(t); } class movable { movable(movable&); movable & operator=(movable&); public: operator rv_ref<movable>() { return rv_ref<movable>(*this); } operator const rv_ref<movable>() const { return rv_ref<movable>(*this); } movable() : i(0) {} movable(rv_ref<movable> rv) { movable &t = rv.get(); i = t.i; t.i = 0; } movable& operator=(rv_ref<movable> rv) { movable &t = rv.get(); i = t.i; t.i = 0; return *this; } int i; }; movable sm_rvalue() { movable m; return move(m); } int main() { movable m, m2(move(m)); m = move(m2); //MSVC 7.1 //error C2679: binary '=' : no operator found which //takes a right-hand operand of type 'movable' (or //there is no acceptable conversion) //GCC //error: no matching function for call to 'movable::movable(movable)' //note: candidates are: movable::movable(rv_ref<movable>) //note: movable::movable(movable&) m = sm_rvalue(); return 0; }