On Nov 16, 2009, at 7:46 AM, David Abrahams wrote:
On Sep 8, 2009, at 5:52 AM, Ion Gaztañaga wrote:
We need a third alternative: a new overload set that maintains "const T &" and properly catches non-const rvalues.
I think we have it:
define one copy assignment operator in terms of swap. Copy elision makes it nearly as fast as a move, and we don't get an operator=(T&) infection in derived classes.
I have no problem with requiring move-enablers to supply a swap.
In fact, I don't even think we need to do that. This seems to work pretty well: #define BOOST_COPYABLE_AND_MOVABLE(TYPE)\ public:\ TYPE& operator=(TYPE t)\ { return this->operator=(static_cast< ::boost::rv<TYPE>&>(t)); } \ public:\ operator ::boost::rv<TYPE>&() \ { return *reinterpret_cast< ::boost::rv<TYPE>* >(this); }\ operator const ::boost::rv<TYPE>&() const \ { return *reinterpret_cast<const ::boost::rv<TYPE>* >(this); }\ private:\ // -- David Abrahams BoostPro Computing http://boostpro.com