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  1. #include <iostream>
  2. #include <utility>
  3. #include <array>
  4. #include <tuple>
  5.  
  6. using ID = unsigned int;;
  7. ID const maxID = 1<<8;
  8.  
  9. template <typename... Ts>
  10. struct SOA {
  11.   std::tuple< std::array< Ts, maxID >... > a;
  12.   ID currentMaxID = 0;
  13. };
  14.  
  15. template<unsigned...>struct indexes{using type=indexes;};
  16. template<unsigned Max, unsigned...Is>struct make_indexes:make_indexes<Max-1,Max-1,Is...>{};
  17. template<unsigned...Is>struct make_indexes<0,Is...>:indexes<Is...>{};
  18. template<unsigned Max>using make_indexes_t=typename make_indexes<Max>::type;
  19. template<class T>using decay_t=typename std::decay<T>::type;
  20.  
  21. namespace details {
  22.   template <typename... Ts, unsigned... Is>
  23.   ID AddEntity(indexes<Is...>, SOA<Ts...>& soa, decay_t<Ts> const&... ts) {
  24.     int unused[] = { ( (std::get<Is>(soa.a)[soa.currentMaxID] = ts), void(), 0 )..., 0 };
  25.     (void)(unused);
  26.     return soa.currentMaxID++;
  27.   }
  28.   template <typename... Ts, unsigned... Is>
  29.   void RemoveEntity(indexes<Is...>, SOA<Ts...>& soa, ID entityID) {
  30.     --soa.currentMaxID;
  31.     int unused[] = {
  32.       ( (std::get<Is>(soa.a)[entityID] = std::get<Is>(soa.a)[soa.currentMaxID]),
  33.       void(), 0 )..., 0
  34.     };
  35.     (void)(unused);
  36.   }
  37. }
  38. template <typename... Ts>
  39. ID AddEntity(SOA<Ts...>& soa, decay_t<Ts> const&... ts) {
  40.   return details::AddEntity( make_indexes_t< sizeof...(Ts) >{}, soa, ts... );
  41. }
  42.  
  43. template <typename...Ts>
  44. void RemoveEntity(SOA<Ts...>& soa, ID entityID) {
  45.   details::RemoveEntity( make_indexes_t< sizeof...(Ts) >{}, soa, entityID );
  46. }
  47. int main() {
  48. 	SOA<int, double> test;
  49. 	AddEntity( test, 0, 3 );
  50. 	RemoveEntity( test, 1 );
  51. 	// your code goes here
  52. 	return 0;
  53. }
Success #stdin #stdout 0s 3292KB
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https://ideone.com/KoCpB1
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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