c++17

c++17

std::invoke

#include <iostream>
#include <functional>    //c++17 std::invoke

using namespace std;
class MyClass {
public:
    int memberVariable = 10;
    void memberFunction(int a, int b) {
        std::cout << "Member function called! a:" << a << " b:" << b << std::endl;
    }
};

int main() {
    MyClass obj;

    // 使用 std::invoke 调用成员函数指针
    void (MyClass::*funcPtr)(int,int) = &MyClass::memberFunction;
    std::invoke(funcPtr, obj,10,20);

    // 使用 std::invoke 访问成员对象指针
    int MyClass::*v = &MyClass::memberVariable;
    int value = std::invoke(v, obj);

    std::cout << "Value: " << value << std::endl;

    return 0;
}

#include <iostream>
enum TYPE{A = 1, B = 2, C = 3, D = 4, E = 5 };

template<typename... Args>
constexpr qlonglong mergeType(Args... args)
{
    qlonglong ret = 0;
    ((ret = (ret << 4) | args), ...); //c++17折叠表达式
    return ret;
}

int main() {
	// ((A << 4) | B) << 4 | C ...
    auto num = mergeType(A, B, C, D, E);
    do {
      std::cout << "type=" << (num & 0xF) <<std::endl;
    } while(num >>= 4);
}