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  1. #include <iostream>
  2. #include <memory>
  3. #include <utility>
  4.  
  5. struct A {
  6.     A(int&& n) { std::cout << "rvalue overload, n=" << n << "\n"; }
  7.     A(const int& n) { std::cout << "const  overload, n=" << n << "\n"; }
  8.     A(int& n)  { std::cout << "lvalue overload, n=" << n << "\n"; }
  9. };
  10.  
  11. class B {
  12. public:
  13.     template<class T1, class T2, class T3>
  14.     B(T1&& t1, T2&& t2, T3&& t3) :
  15.         a1_{std::forward<T1>(t1)},
  16.         a2_{std::forward<T2>(t2)},
  17.         a3_{std::forward<T3>(t3)}
  18.     {
  19.     }
  20.  
  21. private:
  22.     A a1_, a2_, a3_;
  23. };
  24.  
  25. template<class T, class U>
  26. std::unique_ptr<T> make_unique1(U&& u)
  27. {
  28.     return std::unique_ptr<T>(new T(std::forward<U>(u)));
  29. }
  30.  
  31. template<class T, class... U>
  32. std::unique_ptr<T> make_unique2(U&&... u)
  33. {
  34.     return std::unique_ptr<T>(new T(std::forward<U>(u)...));
  35. }
  36.  
  37. int main()
  38. {   
  39.     auto p1 = make_unique1<A>(2); // rvalue
  40.     int i = 1;
  41.     auto p2 = make_unique1<A>(i); // lvalue
  42.  
  43.     std::cout << "B\n";
  44.     const int& j = i;
  45.     auto t = make_unique2<B>(2, i, j);
  46. }
Success #stdin #stdout 0.01s 5400KB
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stdin
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Standard input is empty
stdout
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rvalue overload, n=2
lvalue overload, n=1
B
rvalue overload, n=2
lvalue overload, n=1
const  overload, n=1
https://ideone.com/HAgnMe
language:
C++14 (gcc 8.3)
created:
2 years ago
visibility:
public

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