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  1. #include <iostream>
  2.  
  3. class nullparam
  4. {};
  5.  
  6. template <class T, T Default>
  7. class default_param
  8. {
  9. public:
  10. 	default_param (const nullparam&)
  11. 		:	_value (Default)
  12. 	{}
  13.  
  14. 	default_param (const T& val)
  15. 		:	_value (val)
  16. 	{}
  17.  
  18. 	default_param (T&& val)
  19. 		:	_value (std::forward <T> (val))
  20. 	{}
  21.  
  22. 	const T& get () const
  23. 	{
  24. 		return _value;		
  25. 	}
  26.  
  27. private:
  28. 	T _value;
  29. };
  30.  
  31.  
  32. void foo (default_param<int, 10> p1, default_param <short, 22> p2, default_param <char, 'H'> p3)
  33. {
  34. 	std::cout << p1.get () << ' ' << p2.get() << ' ' << p3.get() << std::endl;
  35. }
  36.  
  37. int main() {
  38.  
  39. 	foo (nullparam(), nullparam(), 'G');
  40. 	foo (155, nullparam(), nullparam());
  41. 	foo (nullparam(), 122, nullparam());
  42.  
  43. 	return 0;
  44. }
Success #stdin #stdout 0s 3296KB
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stdin
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Standard input is empty
stdout
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10 22 G
155 22 H
10 122 H
https://ideone.com/mT7z0z
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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