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  1. #include <iostream>
  2. #include <vector>
  3. #include <string>
  4.  
  5. template <typename, typename>	
  6. struct foo_Impl;
  7.  
  8. template <typename T>
  9. class A
  10. {
  11. public:
  12.   template <typename U>
  13.   void foo() const { foo_Impl<T, U>(*this); }
  14.  
  15. private:
  16.   template <typename, typename>	
  17.   friend struct foo_Impl;
  18.  
  19.   void print(const std::string& text) const
  20.   {
  21.   	std::cout << this << ": " << text <<std::endl;
  22.   }
  23. };
  24.  
  25. template <typename T, typename>	
  26. struct foo_Impl
  27. {
  28.   foo_Impl(const A<T>& owner) { owner.print("general implementation"); }
  29.  
  30. };
  31.  
  32. template <typename T>
  33. struct foo_Impl<T, double>
  34. {
  35.   foo_Impl(const A<T>& owner) { owner.print("specialization for double"); }
  36. };
  37.  
  38. template <typename T, typename U>
  39. struct foo_Impl<T, std::vector<U>>
  40. {
  41.   foo_Impl(const A<T>& owner) { owner.print("specialization for vectors of all types"); }
  42. };
  43.  
  44. int main() {
  45.  
  46.   A<int> a;
  47.  
  48.   a.foo<int>();
  49.   a.foo<double>();
  50.   a.foo<std::vector<bool>>();
  51. }
Success #stdin #stdout 0s 15240KB
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Standard input is empty
stdout
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0x7ffc890570ef: general implementation
0x7ffc890570ef: specialization for double
0x7ffc890570ef: specialization for vectors of all types
https://ideone.com/FNbuG3
language:
C++ (gcc 8.3)
created:
4 years ago
visibility:
public

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