1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
|
#include <iostream>
using namespace std;
class Demo
{
public:
Demo() = default;
Demo(Demo const &other)
{
cout << "Copy constructor\n";
}
Demo(Demo &&tmp)
{
cout << "Move constructor\n";
}
Demo &operator+=(Demo const &rhs) &&
{
cout << "Move +=\n";
return *this;
}
Demo &operator+=(Demo const &rhs) &
{
cout << "Copy +=\n";
Demo tmp{ *this };
std::move(tmp) += rhs;
swap(tmp);
return *this;
}
void swap(Demo &rhs)
{}
};
Demo &&operator+(Demo &&lhs, Demo const &rhs)
{
cout << "move operator+\n";
lhs += rhs;
cout << "move operator+ returns\n";
return move(lhs);
}
Demo &&operator+(Demo const &lhs, Demo const &rhs)
{
cout << "copy operator+\n";
Demo tmp{ lhs };
// tmp += rhs;
cout << "copy operator+ returns\n";
return move(tmp += rhs);
return move(tmp);
}
int main()
{
Demo d1;
d1 + d1 + d1;
cout << "========\n";
Demo{} + d1 + d1;
}
|
