Nice. I think we'd implement a "move" function which could handle that explicitly in any real implementation: Y(ref rhs) : X( move(*rhs.p) ) // <== here , id(++cnt) , owner(rhs.p->owner) { std::cout << "MOVE #" << id << " <== #" << rhs.p->id << std::endl; rhs.p->owner = false; assert(owner); } ========================================== Gary > Thank you! I must be dense but I'm not seeing how a move function would give us the right type. template<class T> ??? move(T &) {... } X( move (*rhs.p) ) // T is a Y // calls X copy if move returns T *. and we need X ( X::ref) // and X::ref only takes a X * and X::ref private to X. What am I missing here? ==========================================

All in all I like it better than the MOJO soln which IMO was much more invasive.

What about the MOJO approach seems more invasive to you? =========================================== Gary > Well you need to modify both the functions you use and the class. And the class requires more modification. class Y : public ::mojo::enabled<Y> { ..... Y &operator=(Y const & rhs) // source is a non const lvalue { using ::std::swap; Y tmp(rhs); tmp.swap(*this); return *this; } Y &operator=(::mojo::temporary<Y> src) // source is a temporary { src->m_ptr.swap(m_ptr); src->release(); return *this; } Y &operator=(::mojo::fnresult<Y> src) // source is a fn result { return operator=(::mojo::temporary<Y>(src)); } ..... }; // Special return type from an object to use it.... // test with binary operator + ::mojo::fnresult<Y> operator +(Y lhs, Y const &rhs) { return lhs; // do the addition here } vs with move.cpp, no special type necessary.... Y operator + (Y lhs, Y const &rhs){ return lhs; // do the addition here. } I have source code that does a similar set of tests with mojo.h as I did for move.cpp if you want to look at it. Yours, -Gary- powellg@amazon.com