Slicing: Copying a Derived Object Into a Base

1#include <iostream>
2#include <string>
3using namespace std;
4 
5class Shape {
6public:
7    virtual string kind() const { return "shape"; }
8    virtual ~Shape() {}
9};
10 
11class Square : public Shape {
12public:
13    string kind() const override { return "square"; }
14};
15 
16void byValue(Shape s) {
17    cout << s.kind() << endl;
18}
19 
20void byRef(const Shape& s) {
21    cout << s.kind() << endl;
22}
23 
24int main() {
25    Square sq;
26    Shape copy = sq;
27    cout << copy.kind() << endl;
28    byValue(sq);
29    byRef(sq);
30    Shape* p = new Square;
31    cout << p->kind() << endl;
32    delete p;
33    return 0;
34}