template<C>
class parent {
public:
   int asdf;
 
   C parent::operator-(){
      T ret;
      ret.asdf *= -1;
      return ret;
   }
};
class A : public parent<A> {};
class B: public parent<B> {};
 
int main(){
   A a;
   a.asdf = 2;
   A b = -a;
}