Not if they have just the same value, but if they're the same memory location. So check the pointers: void swap(T &x, T &y) { if (&x == &y) return; x

Not if they have just the same value, but if they're the same memory location. So check the pointers: void swap(T &x, T &y) { if (&x == &y) return; x ^= y; y ^= x; x ^= y; }