程序完善填空：以下程序是实现一个安全计数器，防止溢出。 #include #include using namespace std; class Calculator{ public: Calculator() { value = 0 ; } ; void ______ ++ (); void operator -- (); unsigned int operator() (); private: unsigned ______ value; }; void Calculator ______ operator ++ (){ if ( value < 65535 ) value ++ ; else { cout << "\nData overflow !" << endl ; abort() ; } } void Calculator::operator --(){ if ( value > 0 ) value -- ; else{ cout << "\n Data overflow !" << endl ; abort() ; } } unsigned int Calculator::operator() (){ ______ value ; } int main(){ Calculator ______ ; int i ; for( i = 0 ; i < 5 ; i ++ ){ ++Counter ; cout << "\n Counter = " << Counter() ; } for( i = 0 ; i <= 5 ; i ++ ){ --Counter ; cout << "\n Counter = " << Counter() ; } return 0; }