own Error-Class (Basics)

class neg_sum{};

int main(){
  try {
.     ...
.     
.     ...
  } catch(neg_sum const & e){
.     std::cout << "negative value"<<"\n";
  }   
}

In der Funktion

double solve_quadratic(int a, int b, int c) {
    double delta = pow(b, 2) - (4 * a * c);
    if (delta < 0) {
        throw Negative_delta{};
    }
.   .....
}