C++ final的用法

// Online C++ compiler to run C++ program online
#include <iostream>

struct Base {
    virtual void print_val() {
        std::cout << val << std::endl;
    }
    double val;
    int num;
};

struct A final : Base {
    void print_val() final{
        std::cout << val+1 << std::endl;
    }
    void print_num() // final // error: print_num not virtual
    {
        std::cout << num+1 << std::endl;
    }
};

int main() {
    // Write C++ code here
    std::cout << "Hello world!";

    return 0;
}