#include <iostream>

template <typename T, std::enable_if_t<std::is_arithmetic<T>::value, T> = 0>
void swap(T &x, T &y) {
  x += y;
  y = x - y;
  x -= y;
}

int main() {
  char x = '[';
  char y = 'w';

  swap(x, y);

  std::cout << "x = " << x << ", y = " << y;

  return 0;
}