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  1. #include <stdlib.h>
  2. #include <iostream>
  3. #include <map>
  4. #include <typeindex>
  5.  
  6. using namespace std;
  7.  
  8. struct Variant{
  9. 	template <class T>
  10. 	static Variant* Create(){
  11. 		Variant *v = new Variant();
  12. 		v->m_data = malloc(sizeof(T));
  13. 		v->m_size = sizeof(T);
  14. 		return v;
  15. 	}
  16. 	~Variant(){
  17. 		free( m_data);
  18. 	}
  19.  
  20. 	template <class T>
  21. 	T &get(){
  22. 		return *reinterpret_cast<T*>(m_data);
  23. 	}
  24.  
  25. 	//copy ctor, etc...
  26. private:
  27. 	void *m_data;
  28. 	size_t m_size;
  29. };
  30.  
  31. struct Foo{
  32. 	template<class T>
  33. 	T &get(){
  34. 		static const char addr = '\0';
  35. 		auto it = m_data.find(&addr);
  36. 		if(it != m_data.end()){
  37. 			return it->second->get<T>();
  38. 		}
  39. 		Variant *val = Variant::Create<T>();
  40. 		m_data[&addr] = val;
  41. 		return val->get<T>();
  42. 	}
  43. private:
  44. 	map<const char*,Variant*>  m_data;
  45. };
  46.  
  47. int main() {
  48. 	Foo a;
  49. 	Foo b;
  50.  
  51. 	a.get<int>() = 3;
  52. 	a.get<float>() = -5.5f;
  53.  
  54. 	b.get<int>() = 4;
  55. 	b.get<float>() = -6.5f;
  56.  
  57. 	cout << a.get<int>() << "," << a.get<float>() <<endl;
  58. 	cout << b.get<int>() << "," << b.get<float>() <<endl;
  59.  
  60. 	return 0;
  61. }
Success #stdin #stdout 0s 3432KB
comments ()
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Standard input is empty
stdout
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3,-5.5
4,-6.5
https://ideone.com/MMPhYa
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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