Hi boosters, We often need to swap contents of two objects, but even more often we need to swap contents with no-throw exception guarantee. But currently we have no general way to swap two objects with no-throw exception guarantee. What we do have now is std::swap, and member functions which can be named swap, Swap, and so on. But now we can't swap arbitary types with no-throw exception guarantee in a general way. Yes, we can overload std::swap to support other than std:: types, but we can't guarantee that invocation of std::swap won't throw. So, I propose the following: New traits classes: boost::is_swappable<T>::value, boost::is_nothrow_swappable<T>::value. and specialize them for known types, but by default both should return false. Introduce new function boost::nothrow_swap(T &, T &); which will swap two objects if boost::is_nothrow_swappable<T>::value == true, else compile-time error will occur. Introduce new function boost::swap(T &, T &); which will swap two objects if boost::is_swappable<T>::value == true, else compile-time error will occur. Introduce template<typename T> struct do_nothrow_swap { static void nothow_swap (T &, T&); } and specialize it for types that can be swapped with no-throw guarantee such as std::vector, invoking default implementation will lead to compile-time error. Introduce template<typename T> struct do_swap { static void swap(T &, T &); }; and specialize it for types that can be swapped(but without guarantees) such as boost::array, invoking do_nothow_swap<T>::nothow_swap if no specialization found. Using this technique, we can support even such classes that doesn't have swap member-function, but have Swap or any other. I guess it would be helpful at least in boost::ptr_container library. This gives new standard way to do the swapping work, and in contrast to std::swap now we can be expilictly specify no-throw guarantee if needed. As always any comments are appreciated. P.S. Sorry if it was already proposed, didn't found it. -- Pavel Chikulaev