fork download
copy 
  1. #include <iostream>
  2. #include <type_traits> 
  3.  
  4. template<int I,class T> 
  5. struct static_case { 
  6. 	static constexpr int value = I; 
  7. 	using type = T; 
  8. };
  9.  
  10. template<int I, class DefaultType, class Case1, class... OtherCases> 
  11. struct static_switch{ 
  12. 	using type = typename std::conditional< I==Case1::value ,  
  13. 					typename Case1::type, 
  14. 					typename static_switch<I,DefaultType,OtherCases...>::type 
  15. 				     >::type; 
  16. }; 
  17.  
  18. struct fail_on_default {};
  19.  
  20. template<int I, class DefaultType, class LastCase> 
  21. struct static_switch<I,DefaultType,LastCase> { 
  22. 	using type = typename std::conditional< I==LastCase::value ,  
  23. 					typename LastCase::type, 
  24. 					DefaultType
  25. 				     >::type;
  26.  
  27. 	static_assert(!(std::is_same<type, fail_on_default>::value),
  28.                   "Default case reached in static_switch!");
  29. }; 
  30.  
  31.  
  32. template<class T>
  33. typename static_switch<sizeof(T)
  34.         	,fail_on_default // default case
  35.             ,static_case<sizeof(long long),long long>
  36.             >::type foo(T bar){ return reinterpret_cast<decltype(foo(bar))&>(bar);}
  37.  
  38. struct test{
  39. 	int a,b,c;
  40. };
  41.  
  42. auto val = foo(13.0);
  43. //auto val = foo(test());
  44. static_assert(std::is_same<long long, decltype(val)>::value,"Not converted to long long!");
  45.  
  46. using namespace std;
  47.  
  48. int main(){ 
  49. 	// your code goes here
  50. 	return 0;
  51. }
Success #stdin #stdout 0s 3092KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
Standard output is empty
https://ideone.com/68KwUq
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!