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  1. #include <iostream>
  2.  
  3. using namespace std;
  4.  
  5. template <typename Derived> struct base
  6. {
  7.   void interface()
  8.   {
  9.     static_cast<Derived*>(this)->implementation();
  10.   }
  11.   void implementation()
  12.   {
  13.     cout << "Default\n";
  14.   }
  15. };
  16.  
  17. struct overrider : base<overrider>
  18. {
  19.   void implementation()
  20.   {
  21.     cout << "Overridden\n";
  22.   }
  23. };
  24.  
  25. struct nonoverrider : base<nonoverrider>
  26. {
  27. };
  28.  
  29. template <typename twicederived> struct derived : base<twicederived> 
  30. {
  31.   void implementation()
  32.   {
  33.     cout << "Derived Base\n";
  34.   }
  35. };
  36.  
  37. struct twicederivednonoverrider : derived<twicederivednonoverrider>
  38. {
  39. };
  40.  
  41. struct twicederivedoverrider : derived<twicederivedoverrider>
  42. {
  43.   void implementation()
  44.   {
  45.     cout << "Derived overridden\n";
  46.   }
  47. };
  48.  
  49. int main()
  50. {
  51.   overrider overrider;
  52.   nonoverrider nonoverrider;
  53.   twicederivednonoverrider twicederivednonoverrider;
  54.   twicederivedoverrider twicederivedoverrider;
  55.  
  56.   overrider.interface();
  57.   nonoverrider.interface();
  58.   twicederivednonoverrider.interface();
  59.   twicederivedoverrider.interface();
  60. }
  61.  
Success #stdin #stdout 0s 2896KB
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Standard input is empty
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Overridden
Default
Derived Base
Derived overridden
https://ideone.com/YDFXmp
language:
C++ (gcc 8.3)
created:
10 years ago
visibility:
public

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