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  1. #include <iostream>
  2. #include <type_traits>
  3.  
  4. template<typename T>
  5. void foo(T) { std::cout << __PRETTY_FUNCTION__ << std::endl; }
  6.  
  7. template<typename T>
  8. struct pair {
  9. 	pair(T v)
  10. 		:key("")
  11. 		,val(v)
  12. 	{}
  13. 	pair(const char *k, T v)
  14. 		:key(k)
  15. 		,val(v)
  16. 	{}
  17.  
  18. 	const char *key;
  19. 	T val;
  20. };
  21.  
  22. template<typename T>
  23. auto make_pair(const char *key, T &&val) {
  24. 		using R = typename std::conditional<
  25. 			 std::is_rvalue_reference<decltype(val)>::value || std::is_const<decltype(val)>::value
  26. 			,const T&
  27. 			,T&
  28. 		>::type;
  29. 	return pair<R>{key, val};
  30. }
  31.  
  32. int main() {
  33. 	int i=0;
  34. 	auto p0 = make_pair("i", 33);
  35. 	foo(p0);
  36. 	auto p1 = make_pair("i", i);
  37. 	foo(p1);
  38.  
  39. 	foo(make_pair("i", 33));
  40. 	foo(make_pair("i", i));
  41. }
  42.  
Success #stdin #stdout 0s 3096KB
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Standard input is empty
stdout
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void foo(T) [with T = pair<const int&>]
void foo(T) [with T = pair<int&>]
void foo(T) [with T = pair<const int&>]
void foo(T) [with T = pair<int&>]
https://ideone.com/jWmnKj
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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