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  1. #include <iostream>
  2.  
  3. template <typename T>
  4. class X {
  5. public:
  6.     X(T d): y(d) {}
  7.  
  8. private:
  9.     class Y {
  10.     public:
  11.         Y(T d): data(d) {}
  12.  
  13.     private:
  14.         T data;
  15.  
  16.         friend std::ostream &operator <<(std::ostream &os, Y const& y)
  17. 	    {
  18. 	        os << "Y(" << y.data << ")";
  19. 	        return os;
  20. 	    }
  21.     };
  22.  
  23.     Y y;
  24.  
  25.     template <typename U>
  26.     friend std::ostream &operator <<(std::ostream &os, const X<U> &x);
  27. };
  28.  
  29. template <typename U>
  30. std::ostream &operator <<(std::ostream &os, const X<U> &x) {
  31.     os << "X " << x.y;
  32.     return os;
  33. }
  34.  
  35. int main() {
  36.     std::cout << X<int>(1);
  37.     return 0;
  38. }
Success #stdin #stdout 0s 3344KB
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stdin 
Standard input is empty
stdout 
X Y(1)
https://ideone.com/dx8Qri
language:
C++ (gcc 8.3)
created:
11 years ago
visibility:
secret

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