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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. constexpr int n = 100;
  5.  
  6. template<typename T, T swapFor0> class SwappedValT
  7. {
  8. 	T tVal;
  9. public:
  10. 	SwappedValT() = default;
  11.  
  12. 	SwappedValT(T t)
  13. 	{
  14. 		if     ( t == 0 )        { tVal = swapFor0; }
  15. 		else if( t == swapFor0 ) { tVal = 0; }
  16. 		else					 { tVal = t; } 
  17. 	}
  18.  
  19. 	operator T()
  20. 	{ 
  21. 		if     ( tVal == 0 )        { return swapFor0; }
  22. 		else if( tVal == swapFor0 ) { return 0; }
  23. 		else                        { return tVal; } 
  24. 	}
  25. };
  26.  
  27. SwappedValT<int, n> arr[5];
  28.  
  29. int main()
  30. {
  31. 	 SwappedValT<int, n> t1{0}, t2{}, t3;
  32.  
  33. 	 cout << "zero init: " << t1 
  34. 			<< ", default init: " << t2 
  35. 			<< ", uninit: " << t3 
  36. 			<< endl;
  37.  
  38. 	 cout << "element of array with static storage duration = " << arr[2] << endl;
  39.  
  40. 	 // Note how SwappedValT<int, n> behaves just like int for all
  41. 	 // practical purposes. There are limits though with operations 
  42. 	 // on references
  43. 	 // like operator++() though which is not defined.
  44. 	 arr[2] = 3;
  45. 	 arr[3] = n;
  46. 	 arr[4] = 0;
  47.  
  48. 	 cout << "after assigning 3: " << arr[2] << endl;
  49. 	 cout << "after assigning swap val " << n << ": " << arr[3] << endl;
  50. 	 cout << "after assigning 0: " << arr[4] << endl;
  51. 	 cout << "arr elem containing 3 plus 4: " << (arr[2] + 4) << endl;
  52.      return 0;
  53. }
Success #stdin #stdout 0s 3096KB
comments (?)
stdin 
Standard input is empty
stdout 
zero init: 0, default init: 100, uninit: 100
element of array with static storage duration = 100
after assigning 3: 3
after assigning swap val 100: 100
after assigning 0: 0
arr elem containing 3 plus 4: 7
https://ideone.com/wG8yEh
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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