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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. using type_t = int; 
  5. type_t test = 777; 
  6.  
  7. class Base {
  8. public: 
  9. 	Base() : cA(A_var) { A_var = test++; }
  10. 	void demo() { f(); cout << "base:"<<A_var<<endl;  A_var++;}
  11. protected:
  12.     const type_t& cA;
  13. private:
  14.     type_t A_var;
  15.     void f();
  16. };
  17.  
  18. class Derived : public Base{
  19. public:
  20.     void g();
  21. 	void demo() { g(); cout << "derived:"<<cA<<endl; }
  22. };
  23.  
  24. //access in Base class
  25. void Base::f() {
  26.     type_t value = A_var;
  27.     A_var = value;
  28. }
  29.  
  30. //access in Derived class
  31. void Derived::g() {
  32.     type_t value = cA;
  33.     //cA = value; //Error, const reference; good
  34. }
  35.  
  36. class OldBase {
  37. public: 
  38. 	OldBase() { A_var = test++; }
  39. 	void demo() { f(); cout << "base:"<<A_var<<endl;  A_var++;}
  40. private:
  41.     type_t A_var;
  42.     void f();
  43. };
  44.  
  45. int main() {
  46. 	cout << sizeof (Base)<<endl; 
  47. 	cout << sizeof (OldBase)<<endl; 
  48. 	Base b; 
  49. 	Derived d; 
  50. 	b.demo(); 
  51. 	d.demo(); 
  52. 	// your code goes here
  53. 	return 0;
  54. }
Success #stdin #stdout 0s 3460KB
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stdin
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Standard input is empty
stdout
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8
4
base:777
derived:778
https://ideone.com/trn81Z
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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