C++

  
int main() {  
    double num1, num2;  
    char op;  
    cout <<  "请输入第一个数字：";   
    cin >> num1;  
    cout << "请输入运算符（+、-、*、";   
    cin >> op;  
    cout << "请输入第二个数字：";   
    cin >> num2;  
    double result;  
    
    switch (op) {  
        case '+':  
            result = add(num1, num2);  
            break;  
        case '-':  
            result = subtract(num1, num2);  
            break;  
        case '*':  
            result = multiply(num1, num2);  
            break;  
        case '/':  
            result = divide(num1, num2);  
            break;  
        default:  
            cout << "错误：无效的运算符！" << endl;  
            return 0;  
    }  
    cout << "结果：" << result << endl;   
    return 0;  
}