fork download
copy 
  1. #include <iostream>
  2.  
  3. struct B
  4. {
  5.     int type;
  6. 	int val;
  7. 	B(int v) : type(0), val(v) {}
  8. 	B(int t, int v) : type(t), val(v) {};
  9. };
  10.  
  11. struct D1 : public B
  12. {
  13. 	D1(int v) : B(1, v) {}
  14. 	void add100() { val += 100; }
  15. };
  16.  
  17. struct D2 : public B
  18. {
  19. 	D2(int v) : B(2, v) {}
  20. 	void mul100() { val *= 100; }
  21. };
  22.  
  23. void f(B &b)
  24. {
  25. 	using namespace std;
  26.  
  27. 	cout << "pre  = " << b.val << endl;
  28. 	switch (b.type) {
  29. 	case 1:
  30. 		static_cast<D1 &>(b).add100(); // downcast
  31. 		break;
  32. 	case 2:
  33. 		static_cast<D2 &>(b).mul100(); // downcast
  34. 		break;
  35. 	}
  36. 	cout << "post = " << b.val << endl;
  37. }
  38.  
  39. int main(int argc, char **argv) {
  40. 	D1 d1(11);
  41. 	f(d1);
  42.  
  43. 	D2 d2(22);
  44. 	f(d2);
  45. 	return 0;
  46. }
  47.  
  48.  
Success #stdin #stdout 0s 2896KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
pre  = 11
post = 111
pre  = 22
post = 2200
https://ideone.com/MaYOhX
language:
C++ (gcc 8.3)
created:
11 years ago
visibility:
secret

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!