Should copy assignment operator pass by const reference or by value?

Question

Prior to C++11, it has always been the case that copy assignment operator should always pass by const reference, like so:

template 
ArrayStack&         


        

Answer 1

Prior to C++11, it has always been the case that copy assignment operator should always pass by const reference

That is not true. The best approach has always been to use the copy-and-swap idiom, and that's what you're seeing here (although the implementation in the body is sub-optimal).

If anything, this is less useful in C++11 now that you have a move assignment operator too.