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  1. #include <complex>
  2. #include <functional>
  3. #include <utility>
  4.  
  5. template <class A, class B>
  6. class X {
  7. public:
  8.     A a;
  9.     B b;
  10.  
  11.     X(A a, B b) : a(a), b(b) {}
  12.     X(const std::pair<A, B> &value) : a(value.first), b(value.second) {}
  13.  
  14.  
  15.     template <class C,template <typename, typename> typename O >
  16.     friend X<A, C> operator+(const X<A, B> &left, const O<B, C> &right) {
  17.        return left + X<B,C>(right);
  18.     }
  19.     template <class C>
  20.     friend X<A, C> operator+(const X<A, B> &left, const X<B, C> &right) {
  21.        return X<A, C>(left.a,right.b);
  22.     }
  23. };
  24.  
  25.  
  26. int main() {
  27.     X<int, int> a(1, 2);
  28.     X<int, float> b(1, 2.5f);
  29.     std::pair<int, float> c(1, 2.5f);
  30.  
  31.     a + b; // Valid
  32.     a + c; // Works
  33. }
Success #stdin #stdout 0s 4528KB
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https://ideone.com/wLW0lf
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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