Item 25: Consider support for a non-throwing swap(Effective C++)

• Provide a swap member function when std::swap would be inefficient for your type. Make sure your swap doesn't throw exceptions.

• If you offer a member swap, also offer a non-member swap that calls the member. For classes (not templates), specialize std::swap, too.

• When calling swap, employ a using declaration for std::swap, then call swap without namespace qualification.

• It's fine to totally specialize std templates for user-defined types, but never try to add something completely new to std.