int main() { try { Student_info record; record.grade(); } catch (domain_error e) { cout << e.what() << endl; } return 0; }
double grade_aux(const Student_info& s) { return s.grade(); }
bool fgrade(Student_info& s) { return s.grade() < 60; }
int main() { Student_info record; if (record.valid()) record.grade(); return 0; }