std::sort does not always call std::swap

Question

Consider the following code:

#include 
#include 
#include 

namespace my_space
{

struct A
{
    double  a;
           


        

Answer 1

Depending on the type, swapping can be more expensive than a move-assignment (in C++98 a simple assignment). The standard library doesn't have any way to detect these cases. At least in C++11 the solution is clear: implement a move-assignment operator for all classes where you implement swap.