Parallel assignment in C++

#include <iostream>

int main() {
  int a = 4;
  int b = 5;
  a, b = b, a;
  std::cout << "a: " << a << endl
            << "b: " << b << endl;

  return 0;
}

a: 4
b: 5

a: 5
b: 4

a, b = b, a;

a, (b = b), a

std::swap(a, b);

tie(a, b) = make_tuple(b, a);

int a = 4;
int b = 5;

{
    int tmp = a;
    a = b;
    b = tmp;
}

template <typename T1> void ParAssign(T1& Lhs_1, T1 const& Rhs1);
template <typename T1, typename T2> void ParAssign(T1& Lhs1, T2& Lhs2, T1 const& Rhs1, T2 const& Rhs2);
// etc.
ParAssign(a,b,
          b,a);