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  1. #include <iostream>
  2. #include <type_traits>
  3. #include <memory>
  4. #include <string>
  5. #include <vector>
  6.  
  7. using namespace std;
  8.  
  9. template<typename T>
  10. struct move_on_copy 
  11. {
  12. 	move_on_copy(T&& aValue) : value(move(aValue)) {}
  13. 	move_on_copy(const move_on_copy& other) : value(move(other.value)) {}
  14.  
  15. 	T& Value() 
  16. 	{
  17. 		return value;
  18. 	}
  19.  
  20. 	const T& Value() const
  21. 	{
  22. 		return value;
  23. 	}
  24.  
  25. private:
  26. 	mutable T value;
  27. 	move_on_copy& operator=(move_on_copy&& aValue);
  28. 	move_on_copy& operator=(const move_on_copy& aValue);
  29. };
  30.  
  31.  
  32. template<typename T>
  33. auto make_move_on_copy(T&& aValue) -> typename enable_if<is_rvalue_reference<decltype(aValue)>::value, move_on_copy<T>>::type
  34. {
  35. 	return move_on_copy<T>(move(aValue));
  36. }
  37.  
  38. template<typename F>
  39. void invoke(F f)
  40. {
  41.     f();
  42. }
  43.  
  44. // some trials
  45. int main() 
  46. {
  47.    	unique_ptr<int> aPtr(new int(5));
  48. 	auto aPtrMov = make_move_on_copy(move(aPtr));
  49. 	unique_ptr<int> aPtr2(new int(5));
  50. 	auto aPtrMov2 = make_move_on_copy(move(aPtr2));
  51.  
  52. 	auto aPtrLam = [aPtrMov] 
  53. 	{
  54. 		cout << "Ptr value: " << *(aPtrMov.Value()) << endl;
  55. 	};
  56.  
  57. 	auto aPtrMutableLam = [aPtrMov2] () mutable
  58. 	{
  59. 		(*aPtrMov2.Value())++;
  60. 		cout << "Ptr value: " << *(aPtrMov2.Value()) << endl;
  61. 	};   
  62.  
  63. 	invoke(aPtrLam);
  64. 	invoke(aPtrMutableLam);
  65. 	invoke(aPtrMutableLam);
  66.  
  67.  
  68.    return 0;
  69. }
Runtime error #stdin #stdout 0s 3060KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
Ptr value: 5
Ptr value: 6
https://ideone.com/YG37md
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
secret

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