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(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;
}
