How can I change the variable to which a C++ reference refers?

Question

If I have this:

int a = 2;
int b = 4;
int &ref = a;

How can I make ref refer to b after this code?

Answer 1

With C++11 there is the new(ish) std::reference_wrapper.

#include 

int main() {
  int a = 2;
  int b = 4;
  auto ref = std::ref(a);
  //std::reference_wrapper ref = std::ref(a); <- Or with the type specified
  ref = std::ref(b);
}

This is also useful for storing references in containers.