#include <iostream>

#include <string>

#include <vector>

void hf0(std::string &)

{

std::cout << "hf0(left-value) is called" << std::endl;

}

void hf0(std::string &&)

{

std::cout << "hf0(right-value) is called" << std::endl;

}

void test_lvalue_rvalue()

{

std::cout << "\n# test_lvalue_rvalue\n";

std::string x("233");

std::cout << "calling hf0(x): ";

hf0(x);

std::cout << "calling hf0(x+\"3\"): ";

hf0(x + "3");

}

void test_move()

{

std::cout << "\n# test_move\n";

std::string x("233");

std::cout << "before moving, x: " << x << std::endl;

std::string y = std::move(x);

//std::string&& y = std::move(x); // ERROR usage (no exception)

std::cout << "after moving, x: " << x << std::endl;

std::cout << "after moving, y: " << y << std::endl;

}

class Class00 {

public:

int id;

Class00(int id_):id(id_) {

std::cout << "construction(" << id_ << ")" << std::endl;

}

Class00(Class00& a):id(a.id + 23) {

std::cout << "copy(" << a.id << ")" << std::endl;

}

Class00(Class00&& a):id(a.id+233) {

//"delete nullptr" is valid

std::cout << "move(" << a.id << ")" << std::endl;

}

~Class00(){

std::cout << "delete(" << id << ")" << std::endl;

}

};

//use "test" to prevent optimization

Class00 hf1(bool test){

Class00 x(0), y(1);

if (test)

return x;

else

return y;

}

//another better example see https://zhuanlan.zhihu.com/p/55229582

void test_move_construction()

{

std::cout << "\n# test_move_construction\n";

Class00 z0 = hf1(false);

std::cout << "z0.id: " << z0.id << std::endl;

}

// g++ draft_move.cpp -std=c++17 -o tbd00.exe

int main(int argc, char *argv[])

{

std::cout << "# draft_move.cpp" << std::endl;

test_lvalue_rvalue();

test_move();

test_move_construction();

return 0;

}