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  1. #include <iostream>
  2.  
  3. template< typename DT, typename... Bases > // C++11 variadic template
  4. struct CRTP: private Bases...
  5. {
  6. 	friend DT; // C++11 extended friend
  7.     DT func( void ) { return DT(); }
  8. };
  9.  
  10. struct A :
  11.     public CRTP< A > 
  12. {
  13.     int get() { return value; }
  14.     private:
  15.         int value = 4;
  16. };
  17.  
  18. struct B :
  19.     public CRTP< B, A > 
  20. {
  21.     double get() { return value; }
  22.     private:
  23.         double value = 1.1;
  24. };
  25.  
  26. int main()
  27. {
  28.     A a;
  29.     B b;
  30.     std::cout << " a: " << a.get() << " b: " << b.get() << std::endl;
  31.     A aa = a.func();
  32.     std::cout << " aa: " << aa.get() << std::endl;
  33.     B bb = b.func(); 
  34.     std::cout << " bb: " << bb.get() << std::endl;
  35. }
Success #stdin #stdout 0s 3296KB
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Standard input is empty
stdout
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 a: 4 b: 1.1
 aa: 4
 bb: 1.1
https://ideone.com/dBEQ7j
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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